James Smallcombe: There we go. And then I'm going to Ruben and say, please tell us about your neighbors.
Ruben: Thanks James unfortunately they're not technically my lasers, which I wish it was not the case. But that's how it is.
Ruben: So I'd like to talk to you a little bit about new frontiers and optical spectroscopy of radioactive nuclear and there's a couple of things I'll cover.
Ruben: Bit of a general introduction first lay of the land, if you will. What, what is it that we do and and why do we, how do we do it, and why does it matter and then some examples that I would like to share with you.
Ruben: One set of results we obtain on radioactive copper isotopes, then I will follow that up with some work on palladium done here in Finland, where I currently am and then some some exciting work with some interesting future implications as well. I think
Ruben: Before I show any of this. I of course have to acknowledge gratefully the support and the help of many people from all over the world.
Ruben: And also very happy to be able to include quite a few names of people who work on theoretical aspects I really do think that
Ruben: That's important in our fields and it makes our work much better than the sum of the parts. But of course, there's also a whole army of experimentalists to thank you. There really are too many to name. So I'll just stick to naming just the institutions there in the little box.
Ruben: So with that, let's let's kick kick things off and and see what it's all about. So what we're trying to do.
Ruben: As, as I think most people who are listening to this are also doing is we're trying to understand the atomic nucleus.
Ruben: Better we're trying to understand the nuclear many body problem and that's that's quite a challenge for one. It's a quantum mechanical metabolic problems. So that makes it
Ruben: Very difficult to tackle. And on top of that. We're also having to deal with a complication that the nuclear interactions are not in principle known in the nuclear medium. So we sort of have a double whammy of issues that we have to address.
Ruben: And we can make headway in this problem in two complementary ways, if you will, or by combining two approaches and that's of course by combining experimental data with with theoretical developments.
Ruben: And I will specifically talk about one class of experiments that is in general atomic spectroscopy laser spectroscopy, where we try and measure
Ruben: Dipole moments magnetic dipole moments electric quadruple moments and nuclear charge, radio, as well as as nuclear spins.
Ruben: And we can use these observable. We can use this information in combination with various different theoretical approaches in order to to try and learn more about this this this complicated puzzle.
Ruben: And this, this has implications beyond just nuclear structured research which, which I think is in of itself already
Ruben: Plenty interesting, but it also has implications for Astrophysics Neutrino Physics searches for beyond standard model of physics and also some some important applications as well. So in that sense, it's a well connected field which impacts on many different domains of science and
Ruben: Over the years many different models have been made for nuclear structure. And as I said, the challenges.
Ruben: That difficult to describe theoretically because they they're a system of strongly coupled particles with the exact form of this nuclear nuclear interaction and not being exactly known
Ruben: So it's absolutely crucial that we provide experimental inputs to constrain theories be them more
Ruben: Effective theories or really theories that try and lift QC the, all the way up to protons and neutrons. And actually, all the way up to realistic nuclei.
Ruben: Whichever theory, this they all benefit from experimental inputs and from experimental benchmarking and that's where as experimentalists we all, in some sense, come in.
Ruben: Now how do we then do this, and what do we actually, what do you actually measure
Ruben: Essentially. It all revolves around this. This one formula here. Everything can be
Ruben: linked back to this when you look at the atomic excitation spectra of an oven elements of an isotope, there will be, of course, an atomic ground state. And then some set of excited excited states.
Ruben: And the first observation that we can make is that the energy difference between this ground state and is excited state. Well, this will depend on the number of neutrons. That's in inside of the nucleus.
Ruben: This, this blue arrow here or the energy difference between these two states will will change as we add or subtract neutrons from the nucleus. And from this change. We call this the isotope shift.
Ruben: From this isotope shift we can we can hope to extract or we can extract the changes in the mean square charge radius, in essence, that the nuclear size is the first thing we can we can access with our measurements.
Ruben: On top of that, these atomic find structure levels also have what we call hyper find structures. So this is an interaction of the electromagnetic moments of the nucleus and the electron
Ruben: Distribution and this leads to a splitting of these fine structural levels in these sub levels, which you see here, and the size of the split things depends on
Ruben: What we call the hyper find parameters called A or B, etc, which in turn depend on, for example, demonic dipole moments or the electric quotable moment. So by measuring the split things we can infer these these observable as well.
Ruben: And the nice thing of laser spectroscopy is if we get both of these at the same time. So we do a single measurements and principal
Ruben: On on one particular isotope, and we will get these these three parameters out of that measurements and usually we can also either directly or indirectly infer what the nuclear spin is as well.
Ruben: So in general, what do we do in laser spectroscopy. We try and measure these this transition frequency as precisely as possible.
Ruben: Or in the case of when this hybrid find structure these different transitions between this these levels in the high profile manifolds. We try and measure these as precisely as possible. And then we get the nuclear observable and we're well on our way to test your theory.
Ruben: Now if you if you were to have a look at the existing literature and the measurements that have been done over the past decades.
Ruben: You will find that they broadly fall into two categories. And I've tried to illustrate some differences between them on the spot here. So on the x axis.
Ruben: I showed the line with of the measurements which was done and the y axis, the yields of radioactive isotopes that was used in this measurement and you can see essentially two clusters of points which I've also indicated with different colors.
Ruben: One is
Ruben: Broadly caught speaking with call them the in source experiments. So these are experiments where we try and do this later spectroscopy really get the site of the production or as close to it as possible.
Ruben: And particular usually well by definition at the source of your radioactive finding facility and the main advantages gives you is that it allows you to study.
Ruben: Isotopes produced that incredibly low production rates. This is below 10 minus one. So, less than one per seconds is nowadays done
Ruben: Well, if not routinely quite quite regularly. So you can really study the extremes of the production and the extremes of the nuclear landscape.
Ruben: The price you pay. However, it is because you're so close to the production environments. You have to deal with broadening mechanisms temperature high pressures, etc.
Ruben: Which means that the line with that you get. So the width of the residences that you observe our broader of the order of at least two gigahertz or more
Ruben: Snow limits in the best case, the precision. In some cases, it also means you cannot access for instance quotable moments or dipole moments. Sometimes that's not possible with this method or charge radio for that matter.
Ruben: There's a second class of methods which I've shown here in orange and this is predominantly what we call a linear fast beam experiments. There's definitely many exceptions here, but most of these are
Ruben: Our colonialism spectroscopy experiments. And I'll tell you much more about how this method works in a bit, but where you can really be see as a line with is dramatically improved is over the order of a few 10 to 100 megahertz or so.
Ruben: And but what you also see there's essentially none of these dots go much below 1000 per seconds. There's a couple exceptions.
Ruben: But a typical rule of thumb is you need a production rates of 1000 per second or 10,000 per second or so in order to use these methods.
Ruben: And the first example that I will talk about will show you actually adult Atlanta outside of this circle. And that's because we've used a more recent methods which takes some of the lessons learned from in source experiments and translate them into
Ruben: The conditions of the millennial age spectroscopy experiments and I will give you much more detail on how that works. Exactly.
Ruben: If if time permits, I'd also like to discuss
Ruben: Some additional things that we're planning for the future. We're currently trying to improve on this resolution even more. And so to push out adults even further.
Ruben: To stop megahertz precision or line with as well and I will discuss that with some recent results, we had on scanning 45 which is stable for now but
Ruben: We hope to go to radioactive isotopes in the near future as well. So this, this is sort of a picture, you can keep in mind for what I'm about to show you.
Ruben: For the rest, however, I should say. It's a very incomplete picture right it's simplifying things a lot
Ruben: Laser spectroscopy. The community is very active has labs all around the world at basically every radioactive finding facility right now.
Ruben: You will find laser spectroscopy setups and people are doing really, really fascinating developments trying to
Ruben: Be more efficient, more precise or some combination of the two in various ways. And I've made a relatively long list here, and it's
Ruben: Definitely not complete of different approaches that people are using in order to do spectroscopy on on various radioactive systems. So it's a very active fields and I've definitely not done it justice just these few slides so also bear that in mind.
Ruben: So on to some results then and also an explanation of how now exactly colonialism spectroscopy works.
Ruben: Just to give you a little layout. So the experiments. I will show you were done at the I sold the hall for those who are not familiar with it, the most important parts.
Ruben: I will try and highlights. So along these lines here we get 1.4 gig electron volts protons from one of the CERN accelerators.
Ruben: And we impinge this beam on to reading usually uranium carbide targets which will be located approximately here this induces loads of reactions fishing simulation, etc. So a lot of different radioactive isotopes are produced.
Ruben: Because the because of the protons hitting the targets. They are ionized using a variety of different iron sources.
Ruben: And then sent through in this case a high resolution magnetic separated in order to separate them by Master charge. So this gives you a first purification. The first selection process.
Ruben: And this is quite important because this produces I sold it produces such an overwhelming amount of radionuclides you really need to clean up the beam in order for it to be useful for for subsequent experiments.
Ruben: This must select the beam is sent into a radio frequency. Cool, they're a bunch of which I will talk about in a bit, and then can be delivered two different experimental setups.
Ruben: And the one I will talk about is located here is the Chris setup to give you a sense of scale. I've added some dimensions here. So the hall is something like a few 10 meters long here and the Chris setup you should picture as being about five meters long.
Ruben: Now, how does colonialism spectroscopy now work. Well, we take these radioactive ions from our favorite facility. In this case I sold these common with the beam energy of about 30 to 60 kilo electron volts. So within our community, we would call these low energy beings.
Ruben: We Benz these into our beam line and overlap them linearly with one or more laser beams in the case of conventional clinic ledger spectroscopy. There is, there would be only one laser beam.
Ruben: The fact that we overlap or two in the way we do is where the word co linear comes from because they are overlaps clearly what is often done then is the ions are sent through what we call a charge exchange. So this is a little part of the vacuum, vacuum system where we have a relatively
Ruben: Not dense. So the opposite of dense gas of in this case potassium
Ruben: Usually or sodium sometimes. And what happens as the ions fly through a day essentially still one of the electrons of these potassium or sodium
Ruben: Atoms and they become neutral themselves. Hence, hence charge exchange. So, or a child exchange reaction.
Ruben: We often have to do this because optical transitions may not be accessible for the single charged ions and then we need to go to neutral atoms instead
Ruben: Of the items can then interact with the lasers and when this laser is student exactly on on this resonance between these fine structure states which I've introduced before the electrons will jump up and then
Ruben: Shortly after, there will be the excitation and a photon will be limited, and then in conventional lasers clinical a spectroscopy.
Ruben: You would use one or multiple for the multiplier to use in order to detect these fluorescence photons.
Ruben: Then by recording this number of photons as a function of the frequency of the lasers. You can uncover this hyper fine structured pattern. And as you can access all of the observable as you're interested in
Ruben: What's important here is the fact that it's a co linear methods, this is, this is what gives the technique, the higher resolution as compared to for instance in source methods because what happens is
Ruben: At the side of the production ions or atoms are are close to being addressed and they are produced with a certain fixed energy spread
Ruben: And this energy spread in turn will give them a certain velocity spread. Now what that means in practice.
Ruben: Since the ions or atoms are all moving at slightly different velocities in the restroom of those atoms. The laser frequency will be slightly different. Because of the Doppler shift.
Ruben: So if you do spectroscopy on on these low energy beams. What you will find is you will find the broadening of your spectral lines shape.
Ruben: Because the atoms are not all flying with the same velocity. However, if you accelerate them the energy spread doesn't change, but the velocity spread good sort of used quite a bit, because this is
Ruben: A square root function of velocity as function of the energy. So that's where the method gets its high resolution from and also it's quite efficient in the sense that you have 100% overlap between laser and iron or atom beam. So it's also efficient in that sense.
Ruben: It's efficient, as I said, because you can study samples with production rates down to, let's say 1000 or 10,000 per second which is compared to the macroscopic world is my needs.
Ruben: But it's still not a low number either. So one thing that we have done over the past two years. If you is that we've developed a variant of this methods which we call linear resonance ionization spectroscopy.
Ruben: The idea here is, rather than monitoring the fluorescence of the atom. So after it's been excited we will apply a second or third
Ruben: laser pulse and the effect of this is that it will ionized. The atoms. So instead of counting the photons, we will
Ruben: Count how many ions, we produce as a function of the frequency of the first place and discounting, we can do in various ways. The simple ways
Ruben: Is direct detection using using, for example, or micro channel plate system or something along those lines. But you can also do more intricate studies very measured decay radiation. And this isn't particularly useful because it gives us additional
Ruben: Ways to minimize background by gating on specific alpha lines, for instance.
Ruben: The advantage of doing this is twofold iron detection to laser ionization and detection is very efficient.
Ruben: So we can we can go to lower production rates than these few thousand per seconds.
Ruben: And secondly, it's important because it comes with an inherently lower background as well because when you're doing this photon detection, you're not only detecting these fluorescent photons. You're also detecting photons.
Ruben: Which scattered laser light essentially detecting photons which
Ruben: Are there because the laser light hits hits something hits the window at the entrance of the beam, like for instance. All this leads to some some scattered photons which you also detect
Ruben: And the Community's been very good about maximizing this collection efficiency and minimizing the amount of scattered lights that reaches the detectors.
Ruben: But nevertheless, it puts a lower limits on what can be done in terms of signal to backgrounds.
Ruben: And that's again something when when you detect ions and, in particular, when you detect decay radiation. You can do much better than this.
Ruben: And let me put this in very concrete terms. So what do we actually gain and this also allows me to give you a little bit of historical perspective.
Ruben: In my opinion, the most important breakthrough for laser spectroscopy and radioactive findings was absolutely the development of the standard colonialism spectroscopy and you can see the somehow
Ruben: Reflected in this graph here. This shows the number of elements which has been studied using various methods. And you can see here CB that's killing your fast beam spectroscopy.
Ruben: has by far the most about 60 elements have been studied so far and our this this again. This graph is not even not even entirely up to date.
Ruben: So it's been an incredibly important development. The second most important development in my opinion is development of this radio frequency called a bunch of
Ruben: Which I briefly mentioned earlier. So what this allows us to do. It allows us to take a continuous beam as it is produced by by the radioactive iodine facility.
Ruben: And allows it to turn into a bunch of beam and by exploiting this time structure. We can dramatically reduced the background of these conventional linear laser spectroscopy methods and you can see that illustrated here.
Ruben: By by essentially gating on the, the time of flights of the ions. You can see this disproven those single to background is is three or four orders of magnitude. So it's, it's a huge game.
Ruben: And particularly because it only has a very, very minor loss in efficiency if if any at all. So single to background is improved because the background is reduced significantly
Ruben: Now this then allows us to compare this to the methods that I've just discussed. So instead of the directing photons. What happens when you detect laser ions. Instead, you see another factor of 10 or so in signal to background here.
Ruben: So again, the specter are much cleaner, which allows us to one study, for instance, this is copper 72 I think study this more quickly and more easily.
Ruben: But also allows us to go to more exotic isotopes. But the second thing that's important to mention is also the signal also goes up. So it's not just a matter of signal to background. Also, the total efficiency is is higher as well.
Ruben: To show a different example of this. I compare here again to measurement. So one is the linear fluorescence measurements of copper 75
Ruben: This was the most exotic isotope that could be studied using this methods and I believe this is a
Ruben: Maybe not a few days, but definitely more than one day of data, taking was required to get the spectrum signals of background around one to one. This is the spectrum of copper 75 taken in something like half an hour or so.
Ruben: With much better signal to background and much quicker data collection as well.
Ruben: So not only can be studied copper 75, of course, we can go further, we can go to 7677 and even eventually 78
Ruben: So this is three additional literal numbers, which represents roughly three orders of magnitude in production.
Ruben: Rates as well. So it's a dramatic improvements specifically here for copper. But in general, it's a it's a good improvement on the on the sensitivity of the methods 78 copper was produced at about 20 isotopes per second.
Ruben: Which, which I think is today the most sensitive clinical measurement to date hydro solution. Clean your measurements, definitely.
Ruben: And also important to notice is that there were about 10 to the seven contaminant ions per second as well. So the purity of the team is is about one in a million or so. So the method is capable of handling these these kinds of ratios.
Ruben: From the spectra. Then, as I said, we can extract many things from the split things we get dipole moments and quadruple moments which were reported on already. A few years ago.
Ruben: But we can also get these charge radio by seeing how this this pattern shifts as a function of of neutron number and then you can construct these graphs which show the charge radius.
Ruben: In this case, the changes in the main square charge radio as a function of neutral number. And there's a couple of interesting things you can already see
Ruben: So this is general sort of Powerball parabolic trends and then a flattening of the trends as we approach and equal 50 you can understand this. This is a stabilization because we are approaching N equals 50
Ruben: But another thing you can see that's quite interesting. And what was quite surprising for us is if you look at what's called the odd, even, staggering.
Ruben: So that's essentially how much do they even an isotope stick above the trends of the organizers tops and you can see it very well here, for instance.
Ruben: You can see there's an appreciable or even staggering shown here in this insert, but then towards N equals 15 years. This seems to flatten out and within errors even and even disappears.
Ruben: Presumably, that has something to do with the fact that we're approaching and equals 50 but the real
Ruben: Quantitative interpretation is something that requires input from from theory.
Ruben: So we went ahead and contact. It's different theoretical groups and we were lucky enough that two different approaches.
Ruben: Were applicable to our data. So one is an approach to using density functional theory and the other one is balanced, based in medium similarity or a normalization group which is very, very long, which is why I will probably abbreviated to IMS RG or even just violence base from now on.
Ruben: Their nice because they're complimentary density functional theory presents us with the with the global approach in the sense that it can be used from light, all the way to very, very heavy isotopes, so it's it's a really nice tool to study phenomena throughout the nuclear chart.
Ruben: In order to to make these these functional which which are using the calculations you need to somehow constraints certain parameters to experimental data. There are
Ruben: Coefficients in that are not the word. There's no a priori value for so you obtain those by by fitting to data. In essence, and I will discuss
Ruben: Mostly, these, these fans functions which were already. Let's say formulated quite a while ago. But in recent years have seen a bit of a resurgence. And that's because they are they, they they've proven themselves very capable of predicting and reproducing charge radius data.
Ruben: And what's important to note about these things class functional specifically is that they includes
Ruben: Terms, the surface and pairing terms are proportion, there's additional terms which are proportional to the density gradients and what is found that if
Ruben: In this this fitting process if some charge radio data is included the importance of these turns increases by by orders of magnitude.
Ruben: So somehow this this radius data contains a bit of information that is not present in other variables and by including those in the minimization or the optimization of the functions we can really get a very good agreement between the predictions and the measurements.
Ruben: Second Class of methods is this file and space methods.
Ruben: The nice thing here is they they combine the flexibility and the power of the shell model formalism with more microscopically derived and more rigorously justified interactions in a way
Ruben: And and this is nice because there's already been a lot of developments in shell model.
Ruben: Calculations and show model codes, of course. And so this this approach can take advantage of all that work that was done by this community and can inject into that.
Ruben: These, these interactions which are derived using viral effect of field theory, for instance, so they provide the cleaner.
Ruben: And more rigorously justified link between the underlying to CD and the actual proton, neutron interactions that we're trying to study here. And in that sense, it removes a lot of the phenomenology, which is definitely a step forwards as well.
Ruben: So then what does it look like now the top plot here. The, the white symbols are the experimental data.
Ruben: And then in blue and in green. You can see these fans calculations and you can see they were very well right at this level of zoom. At least they were very, very well. I will show a more zoomed in plot later.
Ruben: And you can also then look at these vs. I am so G calculations, but they're so clearly something isn't quite right. These em one point a to point all calculations, for instance, give us a radio. I know they're too small, whereas the pw it gives us radio that are too large.
Ruben: Now these findings we didn't make those for the first time was specifically for copper. This is the first investigation of those. But this is something that's been seen in general.
Ruben: For many other isotopes as well and is related to the whether or not these interactions with these calculations can reproduce the saturation density of nuclear matter.
Ruben: Because if they can, and the fans functional can then you get a good description of total radio, but for these the orange and red here. This is not so much the case. So the fact that there was this mismatch was, wasn't that sense, not a surprise.
Ruben: How to solve that problem though is a bit of an open question in the field right now there's there's some approaches which do a lot better. But nevertheless,
Ruben: There is no clear idea or clear understanding what
Ruben: Exactly. It should be should be addressed. There was a binding energies also show it here for completeness. So the binding energy for nuclear on the again the fans, the FDA does a little better but
Ruben: The violence based calculations also do very well here. So there's not this big mismatch here as, as was the case for the radio.
Ruben: At this point, however, it's nice to zoom in a little and look at the details a bit more. So this is now resuming of that.
Ruben: Data and it's also important here is we're not looking at total radio, but rather looking at the changes. So we've
Ruben: Everywhere subtracted the square radius of copper 65 so this, this allows us to innocence ignore this offsets problem.
Ruben: Of the vs IMS RG calculations and really look at whether or not they get the the finer details right
Ruben: And then we see actually that this, this, this is very, very good the reproduction of both calculations actually is very good.
Ruben: Both the fans and the development space calculations do really well and and even, I would say that that this orange calculation. Does, does the best out of the two of them.
Ruben: And that's an interesting observation, because that means that, okay, there is this problem with total radio, sure, but the smaller, finer details. It actually models models really really well.
Ruben: And we can make, and in my opinion it's even more impressive. If you look at these odd, even, staggering plots, which I've shown earlier. So these are, these, these three point differences of radio and binding energies.
Ruben: For a few reasons. So let me get into the details as to why I think these plots are so interesting. So first of all for binding energies, there is a sort of
Ruben: All the interactions, all the calculations do more or less similarly well. And in that sense, this was perhaps not so not so surprising. However, for radio the differential radio. The three point differences in the radio, we see some interesting things. So one
Ruben: The fans functional here shown in green.
Ruben: doesn't generate appreciable or even staggering at all, whereas the blue data points do. So what's the difference between the two. Well,
Ruben: The blue functional was optimized.
Ruben: Sort of the green functional is optimized without any data on on charge rate at all, whereas the blue one included the differential radio of the calcium isotopes.
Ruben: And so you can see by adding radius data to the pool of fits observable, you can generate this or even staggering. So the mechanism behind or even staggering of charge radio
Ruben: Is not captured by by looking at just binding energies, for instance, and I think this is a probably a message that generalize really well.
Ruben: In a sense that we really need to look at all the observable is that we can get access to in order to really understand the nuclear have any body problem. The best
Ruben: And I think there's this shows is really well. Now, in that context, then it's
Ruben: To me very interesting that these valence space in media message the calculations seem to generate this or even staggering of the radio, out of the box.
Ruben: And that's interesting because there are very few fit parameters when when these interactions are derived and they on top of that they are fits to only data for a less than four. So only on hydrogen and helium.
Ruben: Isotopes essentially. So the microscopic mechanism that generates or that causes this odd, even, staggering is already captured by looking at just very, very light systems, which I think is a very interesting, very interesting observation.
Ruben: Now that was that was copper and an in depth dive at theory as well. But there's much more to talk about here from the experimental point of view.
Ruben: We've got that much more data since then. So the copper experiments was done in 2015 and since then we've studied several more isotopic chains.
Ruben: And you will see here that we've really zoomed in on studying structures need W magic nuclei so copper also 29 protons is just one outside of the nickel quarter W magic nickel core
Ruben: So we've managed to cross n equals 32 with with us in 52 you can say spectrum here then we've studied these two neutron magic numbers with both in the UN 10 recently as well.
Ruben: But there's also technical developments ongoing and these are really focused on further improving our efficiency as best we can, and also making us more capable of handling these
Ruben: Contamination ratios that we sometimes have to deal with. So these are all very interesting and exciting developments and I'm sure in the coming years.
Ruben: There will be me or another seminar speaker will GLAD YOU TELL YOU ABOUT HOW THESE HAVE HELPED US instead. However, I'd like to zoom in on something a little difference
Ruben: How we can test the description of nuclear charge radio even further and that one one idea we had here that he saw was to look at
Ruben: The form nuclei, because all the cases where the fans functional has so far been tested have all been close to W metric systems. So essentially spherical nuclei. And now we might wonder whether or not the formation
Ruben: Plays a role and to what extent it can handle their formation and this ties into what you could call a another frontier for research laser spectroscopy research.
Ruben: And that's so I've talked about the efficiency frontier in some sense you can call it the universality frontier, if you will, or can our methods be applied in general to all different kinds of elements.
Ruben: And if you look at the nuclear charts here you will see that right now that's not the case. There are some pretty clear gaps here.
Ruben: So all the colored squares are dogs that have been studied using laser spectroscopy methods.
Ruben: Then you can see for instance here in this oval. It's completely blank. Also in the heavy region. There's lots of open squares here as well.
Ruben: And the reason for this is, there's two reasons which are which are linked. The reason is because is that these isotopes are hard to produce at
Ruben: At I sold or in general that is old facilities, you need other methods for that and I'll come back to it.
Ruben: But also, but because that even if you can produce these isotopes that atomic structure is really quite complex and that makes it hard to do spectroscopy. So even if you do have that beam studying it is not necessarily, not necessarily easy
Ruben: And I think most of the work on these cases has been done it and you've asked, and there's a long records of studying these so called refractory systems.
Ruben: Molybdenum Israel tantalum, etc. And so this is really a good lab to try and fill those those gaps and try and answer questions related to to nuclei in this in these regions of the charts.
Ruben: And as I said, the reason there's a good reason for wanting to study them we've more or less discussed spherical systems now with this fans density functional theory approach.
Ruben: But we want to investigate what happens as we increase the defamation of the systems and palladium is from from other data. We know it shows some
Ruben: Some significant defamation and the ground states and other nucleotides in this region also quite quite the forums. There's also tracks reality. So these are all things that you might wish to study.
Ruben: And the reason we can do this at the soul is because rather than using a thick targets we use a thin targets. So that's the
Ruben: The reaction product immediately recoil out of the target foil and they are caught by a gas flow.
Ruben: And then guided onwards towards an extraction region and then onwards towards the instrumentation
Ruben: And the reason why we can study refractory systems or chemically reactive systems here is because this is an incredibly fast method. So, in a few milliseconds.
Ruben: These ions are taken out of this castle. So there's essentially no time for any significant chemistry to happen and that gives the methods universal production that makes it a universal production methods.
Ruben: And I'm going to skip, skip over a whole bunch of detail here, I'm just telling you that we produce this palladium and somehow injected it into a conventional colonialist spectroscopy beam line in order to study there that charge radio
Ruben: I show a couple spectra here. So this is stable palladium and these are a few
Ruben: Partial data sets for the radioactive cases for the old mass isotopes. The analysis, a little tricky and is still ongoing.
Ruben: But I can already share with your results for the even even systems where we only expect one peak in the spectrum. And here you can see palladium 118. So that's the most nutrient rich case that we could study in this case.
Ruben: And well, let me just get straight into results, then. So these are the the charge radio that we measure these triangles here and you can see I've plotted
Ruben: Again to to calculations on top. So the standard and is delta our fans. It's the same as before. So the standards did not include any charge radius data during the optimization of the functional whereas this
Ruben: Delta R1 does. And it's also important to say that this implementation here allows also to study the forum systems and i can i can show that here so you can see
Ruben: This is the the binding energy as a function of information parameters. And so you can see as we go away from n equals 50 where we have a spherical minimum towards in this case, for example, n equals 72 we have the form minimum
Ruben: And so this this code and this this calculations are done, allowing for this information to happen. And so we can now look into the details, more and see
Ruben: Studied information that is generated by these calculations and see if they do a good job and matching matching experimental data.
Ruben: In any case, you can see again this delta are functional does does a lot better. And so we're still investigating this deeper and preparing preparing us for publication soon and the theoretical work here was done by by Marcus course the line and also also it at the hospital.
Ruben: So I think I have a little more time left. So I'd like to then
Ruben: Go to this third leg of the talk. And that's essentially on the third frontier, if you will. You could call it the precision frontier.
Ruben: So I've talked about efficiency and I've showed you how we can get more efficient methods and how it allows us to study interesting physics far from stability.
Ruben: I've shown you an example of what it takes, or that we're also currently working on extending our measurements to challenging atomic systems like palladium.
Ruben: Which happens to coincide with with refractory Enos, in many cases, but there's a third axes that you might consider it. And that's the the precision of the measurements and
Ruben: All the measurements. I've shown so far and the vast majority of measurements and literature are sort of in this blue box here.
Ruben: Because they have line with of the order of gigahertz to a few 10 megahertz. So that's sort of the scale, we're at and that allows us to measure these dipole moments quadruple moments.
Ruben: And charge radio, which is what I've talked about more so far. However, if you can improve our precision beyond this level there's other effects which which we can become sensitive to
Ruben: The hyper fine anomaly is one of them, which is sort of, in many cases, a little bit at the boundary between the two. It cannot really be measured in many cases.
Ruben: Using more standard methods. But definitely, if you go towards, for instance, the magnetic optical moments electric X have a couple moments, etc. We definitely need a dramatic improvement in our precision to the order
Ruben: Well by about three or more orders of magnitude and, I believe, and I think our community in general believes that this is this is definitely feasible and I have no doubts that in the coming years, we will start to see results along these lines as well.
Ruben: Dreaming even further. You can also hope that instead of looking at these means square charge radio perhaps at some point we can look at these
Ruben: fourth power of the radius data as well. But this is definitely a longer way of specifically because it's quite a bit harder to get really precise isotope shifts
Ruben: And getting high precision hyper find structured data is is hard but doable but getting to these very precise is dope shift is a different ballgame. So that will take take quite a bit longer.
Ruben: And I just like to put this into context if if you look at what happens in the other communities. So in the atom and iron trapping community in the quantum metrology communities.
Ruben: These people sometimes do measurements which in effect mean they have line with and then precision is way below below kilo hertz or hurts even
Ruben: So that it's definitely possible to push our precision to be much better than it currently is. And there's definitely ways to get there.
Ruben: We just have to figure out how to sort of marry the realities of a radioactive iodine facility with
Ruben: The with these kinds of techniques and that's something that we're, we're going to start to work on. And I would just like to share one relatively quick example with you of how I personally I'm trying to contribute to this and that's by
Ruben: Specifically, I wanted to have a look at, at the next term in this hyper fine structured expansion, because there is, in principle, infinitely many, but the next one that we can we can hope to measure is this octopus moment is this magnetic optical moments parameter
Ruben: Which it's a very long this function f is ridiculously long so I phone, put it on the slide, but in essence, it gives you access to this this third electromagnetic moments.
Ruben: So dipole moments quadruple moment. Something we have some intuition for but then perhaps we can start and measure these optical moments as well. I've asked my master students to try and visualize what that would look like. And this is what what she came up with.
Ruben: I believe it's somewhat mathematically justified, but my, my intuition doesn't really doesn't really allow me to to say much more than, than it looks rather nifty.
Ruben: So now how do you actually measure this, because this, this is a very small perturbation of the hyper fine structure on top of an already small effect.
Ruben: How can we measure it. I'll come back to that in a bit. What do we already know about magnetic optical moments, not much. So far there's been 20 values measures.
Ruben: All of them on stable isotopes. So no data is available. Anything radioactive at all. And I've summarized them here in these two plots.
Ruben: So these are, this is data for all proton nuclei. This is for neutron nuclei. I pretty much know for every one of these agents already for every one of these dots. What I just opened it. So if you have a question about a particular point, I can tell you which isotope. It is
Ruben: And I compare these dots with a very simple sort of back of the envelope single particle estimates for the magnetic optical moment. So these lines, you see here.
Ruben: Basically it answers the question, what is the magnetic optical moments, if it is entirely caused by the, the violence proton or the violence neutron and the entire core all of the other particles are completely and earth and don't play any role.
Ruben: If you answer that question, then you get these lines, and you can see they work reasonably well.
Ruben: Sort of the general trend is there, they tend to get larger. As you increase the spin of the nucleus and
Ruben: The parallel coupling gives you a larger magnetic octopus moment as well. So they more or less work.
Ruben: But there's very clear deviations and there's also a couple of points which which don't really make too much sense. Right, so there's there's still a lot to learn here.
Ruben: And I think it's important that we try and study these because they give us another measure of the monetization distribution inside of the nucleus. And actually, perhaps the first
Ruben: Together with high profile anomaly, the only measure of monetization distribution inside the nucleus which may have important implications for neutron skin studies.
Ruben: Investigating the role of spin quenching means on exchange currency, etc. So it's, it's something that I think if we get to the point where we can develop a systematic overview of these observable.
Ruben: We will we will learn a lot. And so the trick in order to measure these is to actually stop doing laser spectroscopy and is to use lasers in a different way and actually start doing
Ruben: Radio Frequency spectroscopy instead. I've been talking for about 40 minutes now so I won't really go into the details as to as to how it works.
Ruben: But the key message here is by doing radio frequency spectroscopy, the line with you get
Ruben: Is essentially only limited by the time the interaction time between the atoms. And then the radio frequency field, which means for the simple offline setup that
Ruben: I've used for these measurements, a year to about 10 kilohertz line with relatively easily, which is about three orders of magnitude narrower than what you would get with the normal laser spectroscopy methods.
Ruben: I should emphasize this is unstable scandium and this is in a way that is not applicable to radioactive isotopes yet. So it's only the first step, but nevertheless believe it's an important step.
Ruben: And these are some of the spectra, you can get. So this is a spectrum you would get if you just do normal laser spectroscopy. So you can see here frequency, the tuning of the lasers. This is in megahertz. So this is sort of a gigahertz span.
Ruben: If you instead of the laser. The radio frequency spectroscopy. He can see this is still in megahertz. But you see, this is half a mega hertz or so. So these are dramatically narrower lines.
Ruben: I show here, assuming have a couple. So there are about 4040 kilo hertz wides so again this it's about three orders of magnitude or so narrower, which immediately gives you about three years or so order of magnitude in precision.
Ruben: You can get the hyper parameters from this data sets. And I just want to show you here. If you were to do this with optical spectroscopy, you would be hard pressed to go beyond sort of the first digits after the comma.
Ruben: Whereas, in this case, we're at sort of 100 Hertz level precision so better than a part per million for the dipole coefficients. And we also get a non zero value for this octopus coefficient as well. And you can see here
Ruben: I've plotted this result then on top of the graphs which I showed you earlier, the editor about is rather large, as it turns out, scandium is not extremely sensitive to its underlying optical moments.
Ruben: But with precision like like what I've shown here. We can definitely hope to do very precise measurements on other elements in the future and also on radioactive elements, I think.
Ruben: Radioactive isotopes. What I think is also interesting and very important is that we managed to also have a look at this observable from a theoretical point of view again as I said at the start.
Ruben: In our field, we have this very interesting and nice dialogue between theater in experiments. And so we definitely have to extend this also to these octopus moments, these magnetic optical moments.
Ruben: It's a bit of a complex graph, perhaps, but what it shows is for different functions and different
Ruben: Inclusion of different spin, spin interaction terms, for instance, what kind of ranges of values, you would get for dipole moments and magnetic optical moments.
Ruben: The stars indicate those calculations which reproduce the deformation. The experimental the information that we know are the experimental political moment sorry of scanning 45
Ruben: And then you can see the dipole moments sort of scattering arrange which overlaps really nicely with the experimental value which is this thin green line here.
Ruben: But you can also see that the magnetic octopus moments here is about all point 25 whereas in experiments we have something that's that's about a factor of four or so larger
Ruben: Granted, the editor bar is also large but nevertheless, there's a there's a bit of a discrepancy there.
Ruben: So I think this is very interesting and more work needs to be done to fully understand all of this.
Ruben: But I also think in general. It's very good, because it's it's a demonstration that we can start to understand the, the magnetic ization and the monetization distribution of the atomic nucleus in more detail, for example, with, with the FT which is definitely
Ruben: It's, it's nice in that sense, as I said, the if it is a global approach. So we can hope to study a wide range of different isotopes and different elements with this, with this approach.
Ruben: There's a lot of work still to do theoretically and experimentally, but I think it shows extra in progress and and I hope to continue it in the future.
Ruben: So with that, let me let me close up then, looking ahead, I've, I've tried to give you a little bit of an overview of the state of the arts and where it might go in the future.
Ruben: And somebody I would say our, our extra mentally or techniques, keep marching on. They keep getting better.
Ruben: I've given you examples of of how can you push further from stability more exotic system shorter live systems lower production rates. The example I gave was for copper I've
Ruben: Given an example on how we're also as a community, trying to address systems which are difficult because that atomic structure is complex and that was shown to you for palladium.
Ruben: And I've also showing you an example of what I think what I hope is the start of an interesting development in the future.
Ruben: Really trying to improve our precision and get access to observable, which are currently not accessible and given the challenges that we face in our research field, the more observable, we can access the better.
Ruben: And also it's very important to mention that nuclear theory is definitely also keeping up the pace.
Ruben: And confronting theater and experiment, as I think been been vital for us in the past, and I'm sure it will continue to be to be crucial in the future as well. So that's, I think, all I wanted to share with you.
Ruben: That would be happy to take any questions you might have. Thank you. I heard a single a single tapping person.
James Smallcombe: Asked me. I feel
James Smallcombe: I feel awkward if there's not a clam. So our area. Thank you very much, everyone. Have a great quote. So as I said at the start, if you've got a question. Please feel free either go to the participants menu little raise hand button or you can type it down in the chat box will read that out.
James Smallcombe: But what digital plaques.
James Smallcombe: So I've got a customer, get the ball rolling and sorry he covered this, but so you shouldn't as the defamation from measuring ready I in at the palladium.
James Smallcombe: In that region. This certainly in the ruthenium they've got this degree of tracks reality they're interested in. So if you get sensitivity to try a valid in these is that the the water and you talked about developing sensitivity to
Ruben: I mean, that might be. I think that's definitely something. It's an interesting comment so far. We don't really have a signature for tracks reality from the point of optical spectroscopy only through comparison with with model. Can we can we hope to get somewhere, but as definitely interesting
Ruben: I don't know what to be honest, I think it's something that will will have to work on more and then see. So maybe, yeah.
Ruben: Yeah, as I said right now there's not been any measurements of this this parameter
Ruben: So there's no systematics the base ourselves on which doesn't make it easier but yeah hopefully in the future. This is something we should
Ruben: Think about, yeah.
James Smallcombe: We have any other questions.
James Smallcombe: I think Allison was there. So you want to unmute yourself and go ahead, Allison.
Alison: Yes. Is that good. Yeah. Yeah, I will. Thank you. That was a really good overview and a really nice talk. I was interested in in some of the the calculations, because I
Alison: Thought that you said maybe this is wrong, that one of them were you had some parameters that you fixed on mass for a is for. And yet it work or gave a good representation for this system, which is
Alison: Mass 40 something is. Did I understand that correctly that I was quite surprised by that I think
Ruben: Yeah, no, that's absolutely right. So, these all of these, all these methods which which are related to this kidal effective field theory.
Ruben: They all try and construct an interaction and they try and fit the like the the prudent to body terms they try to fit it to body systems and three body terms, the three body systems. So they really constrained themselves to to to very light systems.
Ruben: And then indeed it's an observation that this, this works extremely well, not so much for total radio, as I've shown there's something missing there. But for many other things you might want to look at. Yeah, they do extremely well.
Alison: It's not working systems other than the copper. It's not just coppers are
Ruben: Known as
Ruben: Yeah, it seems to be seems to be pretty pretty universal. Yeah.
Alison: It's really interesting. Thank you.
Ruben: Yeah, sure. So there's been some work. Now I think now that they're really looking at the 10 regions. So in India, and as far as I know, the, the results look equally promising.
Alison: Thank you.
James Smallcombe: Okay, so we've got another question. Andy Do you want to go ahead with your question.
Andy Briscoe: I really good thanks very much for the talk. I also wants to ask about this slide. So that's quite convenient. And I wanted to ask about the odd, even, staggering in the bottom of that figure in the bottom right.
Andy Briscoe: I just wondered whether that orange cave. Does that predict that the staggering goes away. Also, or not. I don't know the answers. I'm just interested
Ruben: You mean here or
Andy Briscoe: Yeah, that little point there.
Ruben: Yeah. So it's not so not so clear the dollar even staggering. It predicts this is smaller than let's say around here.
Ruben: But yeah, our experimental editors are of course sizable as well. So the agreement is in that sense. And that sounds perfect so it's a little smaller than then then it's over here. Yep.
Cool, thanks. Yep.
James Smallcombe: So is the point where you should be saying if you one last question, but struggling with the raise hand button just go ahead and unmute yourself.
Alison: Sorry, James is Allison. Again, I don't know if I'm allowed to second.
James Smallcombe: Question. Go ahead.
Alison: I was just thinking about when you were expanding the series and got this this extra term and the hyper fine explanation and you got this nice what you called a nifty shape that your MSC student worked out.
Alison: Yeah, and I just wanted what what are the the arrows. There are just to show that is that is that one of those sort of, what do you call them rings. Is it a donor T shapes are holding the middle or is it so
Ruben: Yeah, so the the the the somehow this octopus moments. So the dipole moment. You can think of is like you know you have a charge moving in a loop and they
Ruben: Can reach you, a dipole moment.
Ruben: as as as shown.
Alison: Shown here.
Ruben: What do you have for optical magnetic octopus is that you essentially have these kinds of current loops that are configured in such a way
Ruben: That it's not a pure dipole. But somehow there like a angles. And then there's an additional sort of flow.
Ruben: Of charge going in a certain certain way. And so these arrows somehow show that you have these these current loops which are placed at interesting angles, which which generated fuel that's not a pure dipole anymore.
Alison: So it looks, it looks to me a bit like when it goes when you get a, like a yarn of wool and you kind of twisted and you see it in the will shop. I don't know if that means anything to anybody else. But anyway, is that the right sort of lines, you got it all. It's like that and then you
Ruben: Twist. I see. Yeah, yeah.
Ruben: Yeah, that looks like what was made, indeed.
Yeah.
Ruben: It's it's tricky because it's not a simple quantity to visualize what exactly is happening.
Ruben: Luckily, the math sort of works itself out. But the visualization is not so not so clear.
Alison: It's interesting. Thank you.
Ruben: You're welcome.
James Smallcombe: Did you say something that patty. I saw you prefer.
Patrick Regan: To think of the commerce colleagues might have a comment on
Ruben: I'll forward your question to
Patrick Regan: Turn us
Patrick Regan: He might be the
James Smallcombe: Natural question you want to go ahead
Liam Gaffney: Is moving. Sorry to keep you a little longer. I just wanted to know what is the biggest thing. What's the biggest step you need to make to apply RS spectroscopy.
Liam Gaffney: Facility.
Ruben: Yeah, it depends what you're aiming for, I would say. So to get, let's say, to performance, similar to what I've shown here.
Ruben: It's relatively minor. So it requires adding an like a radio frequency interaction region and you could do this for instance in already in a normal clinical ages because could be be mine.
Ruben: So it would require adding let's say half a meter or so of length to your timeline and that would more or less get you there.
Ruben: Already, and you would get to this ballpark. It probably a little worse. Let's say factors to our servers resolution than this.
Ruben: Which already would be great for many cases like Indian business or two that I'm thinking of right now, which you could sort of do do without immediately. And so that's what we're we're setting up here or once covered covered permits.
Ruben: Is what we will do do here in the near near future, if you really want to have something that is more powerful and really allows you to do this.
Ruben: In general, also for for those with less sensitivity to the underlying optical moments.
Ruben: They need to start looking at at trapping techniques and then things get more complex. And so then you're looking at a time scale of several years or
Ruben: You know, up to a decade or so before you could really hope to to do this in yeah with with that level of precision. So, it depends. I think, first results, you could expect within the next few years.
Liam Gaffney: Okay, thanks for is, is something that we can see soon. Thanks.
Ruben: Helps off.
Liam Gaffney: Okay.
James Smallcombe: I don't think there are any other questions. So I still say thank you for giving you a great talk. You're welcome.
Ruben: Happy to do it.
James Smallcombe: And thank you all for joining us. If you want to come back and hear some more great talks.
James Smallcombe: If you come on Wednesday with the student talk session, so that's that's the other link that's hosted by the University of Manchester.
James Smallcombe: And do encourage your students to come along. So that's 3pm this Wednesday. We've got Connor Hamill from the University of Edinburgh, who's going to be talking about the 25 magnesium DP reaction.
James Smallcombe: And if you come back here for plenary session on Friday.
James Smallcombe: We've got Mark speaker from Florida State University, who's going to be talking to us about price has been symmetry around 56 nickel, so please come back and join us for those. So thank you once again everyone, for joining us for another great talk. And thank you bye for now