James Smallcombe: We go. And then I will hand over to Steve and say, please take it away.
S Yates: Okay, thank you very much, James. It's a pleasure to be here. Well, actually, wherever you are. It's a pleasure to be talking with you.
S Yates: As James indicated, I'm going to be talking about how we use fast neutrons to study, study nuclear structure, a couple of applications. One of them to neutrinos couple beta decay. And then also to shape coexistence and the terrain germanium.
S Yates: Now the first thing I want to do is to give you an idea about the reaction we get with these few MTV neutrons. It's primarily in elastic.
S Yates: elastic scattering, but it's the elastic scattering that's interesting to us if this is a fast neutron and I realize it's not moving that fast, then it's going to undergo a reaction with the nucleus. That's going to excite the nucleus and that nucleus is going to cool and
S Yates: Again, right, or conversion electron some radiation. Let me just show that to you again.
S Yates: And hopefully you'll look at this and you'll say that looks very much to me like a compound nucleus or a fusion of operation reaction.
S Yates: And indeed it is these energies. I think you're you can characterize reaction like that. And so basically what we are doing in this reaction that we're starting from the ground state of some of us.
S Yates: Are exciting up with neutron and then from that excited state. Of course, it's going to eventually Decatur. The ground state.
S Yates: It could decay in a single step or in a couple of steps and those two steps can have different brains. And so those are the kinds of things that we're interested in. When we do in last neutron scattering
S Yates: Now, how do we get the neutrons. Well, we do them. We get them from a reaction, usually of protons and tritium gas.
S Yates: This reaction shown here, we call them model energetic, they're not essentially monitor energetic, they may have a spread spread to 50 kilowatt per hundred kilowatts, or something like that.
S Yates: But for all intents and purposes, they are model energetic, we have a cell premium gas. We have a small vendor graphic songwriter.
S Yates: And that the accelerator is shown here. And so if we take the protons from the accelerator into a guest. So, of course, this reaction produces the neutrons.
S Yates: Which then scatter from our sample and of course that excites the sample who saw in the previous gram and eventually it's going to decay and end up back in the ground state.
S Yates: So this is just a very simple picture or I should say this is a photograph of how we do these measurements in the laboratory.
S Yates: We have a beam protons again into our ESL learners are scattering sample. There's our gas handling system and behind the scattering sample is a germanium detective. It's located more than a meter away.
S Yates: This is another photograph from the side of the experimental arrangement components we had before the beam guess
S Yates: Scattering sample, you'll see there's there's massive amount of shielding because, of course, we want to protect the Romanian detector from indirect neutrons. We know that
S Yates: Electrons damage germanium detectors. So our executives there and we have it surrounded by biggio shield and also see that the equipment is mounted on a movable Bonnie Ahmet or so we can do measurements of various angles. What's not so obvious, is there's also a fault for here.
S Yates: This is just a
S Yates: Thin floor that neutrons produced in the reaction that we don't want scattering into our measurements, they will go down a couple of meters before they scatter. So this was a good design of our laboratory
S Yates: It was designed for neutron measurements and neutrons, of course, have many pernicious effects and we try to avoid as possible.
S Yates: So the first measurement we typically do when we're studying a nucleus is an expectation function.
S Yates: And I've shown here three specter overlaid one at 1.6 another 1.7 a third of 1.8 MTV. And you can see that these peaks grow in as you exceed the threshold for the the
S Yates: Emirates, and you can see that for this gamma ray in particular I 1.6 MTV, the yield is very low. It increases. And so you can extrapolate down to the threshold and you can determine the energy of the meeting state. The same thing you could do for this.
S Yates: The next slide shows an even
S Yates: Better way to get information from the these reactions. You can see that there are two states here. There's been zero plus into plus now about 50 K be apart.
S Yates: And you can see that, of course, when you look at the excitation functions you can extrapolate them down. They both occur around 2.7 and movie.
S Yates: But if you look at the magnitude of the cross sections. You can see that there are decidedly different and so you can use the magnitude of the reaction cross sections to learn about the spam, that's not the only way we get the sense of the level, but it is a very helpful tool.
S Yates: We can also measure and redistribution. Remember these are
S Yates: Fusion evaporation reactions. And so if, in this particular case, we've got a one decay. In this case we've got a scratch to
S Yates: This case we've got zero plus state which we can orient so you can learn a lot about the angular distributions and the alignments. And these reactions can be quite large.
S Yates: Now, this, this shows a angular distribution from one of our major molten iron
S Yates: I actually wish we had taken this much longer to get better statistics because the reason I like to show this one is that the mixing ratio, the two and one mixing ratio for this.
S Yates: Particular decay is very well known and see it's shown over here from the NBC and you can see that our measurement is fairly consistent with that. And so we can get the
S Yates: Mixing ratios and I just put this one in here because it's very
S Yates: Very interesting one to us when we first saw this angular distribution we said we've got a square. Well, it's not a square. Well, it's just a mixing ratio that's very large and positive and again this is in the Romanian
S Yates: So all of these things contribute to what we can learn from unless the neutron scattering
S Yates: We can also observe the Doppler shift.
S Yates: The recall velocities from the recoiling nuclei are not large. But if you have a nucleus, which is recording when some velocity be
S Yates: And you detect the gamma ray while it's moving at TechCrunch some angle theta, then the energy is given by this expression where you have the rest energy plus the energy that you get from the doc promotion.
S Yates: But the nucleus is really recoiling into viscous meaning.
S Yates: What is that viscous medium. Well, it's the other nuclei. And so that it's correct to say that this is time to cram in the quantity
S Yates: And so if we modify this equation, we get the following one where the F of tell factor. The so called attenuation factor now contains the information about the half life.
S Yates: And if we know how to describe the slowing down process, we can extract lifetime needs a Doppler shift attenuation measurements. And so what I've shown on this slide.
S Yates: Is actually three spectra super impose one is measured to 40 degrees. This would correspond to a blue ship where she can see the gamma ray admitted in the direction of the recording. Yes.
S Yates: One of them is a redshift this course, being a backward direction. The other ones in 90 degrees. And you can see that the shifts in each of these specter are different.
S Yates: And that's because of course they have different lifetimes one with the shorter lifetime has the larger shift and the one with the longer lifetime has a smaller ship.
S Yates: So by such measurements we can determine lifetimes. If we know something about stopping process. And so if we were to plot the
S Yates: The gamma ray energy there emitted photon energy is a functional post on angle than the F tell value is going to be given by the slope of this curve.
S Yates: And if you have then then you know something about the stopping process, the calculated curve indicated here you can determine the lifetime. And so our approach for many years has been a somewhat
S Yates: traditional approach. We think we understand these lifetime measurements for well Thomas value develop the formalism for that. And it's describing this reference at the bottom of the slide.
S Yates: And I do have to show one of our better a lifetime measurements. This is a lifetime measurement of
S Yates: Two plus stayed in germanium 74 and you can see that the data or in the beautiful I put preliminary on here because we haven't published this yet, so please don't accept those as a final numbers are probably pretty good but
S Yates: Certainly should not be quoted as such. And you can see that the lifetime measured here is 28 plus minus two seconds. And again, it's just a very pretty measurement
S Yates: The other thing you'll notice is from the forward direction to the backward direction, the largest the differences, only three kilograms. So these are small shifts that we can measure them very accurately.
S Yates: So if I were to summarize what we can do from inelastic neutron scattering with accelerator produced neutrons. I
S Yates: Make the following reasons. First of all, there's no cooling barrier and we have variable neutron energies. The neutron energies are given by the incident proton energies. And so in the site. The nucleus to any degree we want
S Yates: We have excellent energy resolution, because we're detecting gamma rays.
S Yates: The process is non selective or statistical we are limited by the amount of momentum you can bring in with these few me be neutrons.
S Yates: So you're not going to be populating I spend states I presented the lifetime determinations by the Doppler shift attenuation method and are a couple of references here, in particular the the secondary these references.
S Yates: Goes to some problem. One might have. We don't understand everything that's happening. I think we have a pretty good control or not.
S Yates: I didn't talk about gamma. Gamma coincidence measurements. Certainly we can do these. And there are a couple of references shown here.
S Yates: Limitations to the method. Well, we're limited for practical purposes to stable nuclear
S Yates: Why is that, well, it's not because the cross sections are small. In fact, in many cases are quite large 10s or hundreds of Melody Barnes.
S Yates: But we are dealing with secondary beings here, the neutrons. And so we need large amounts of material and it always makes things simpler when we have enriched isotopes, we find that in many cases we can lease these new Oak Ridge National Laboratory
S Yates: So from these measurements in a lasting scattering of fast neutron with gamma ray detection. What can we learn
S Yates: We can determine the level scheme that spins and parodies of the levels we can measure gamma ray branching ratios.
S Yates: We can determine motor polarities, we can determine multiple mixing ratios, we can determine the lifetimes lows quantities, we can determine transition probabilities and I can measure cross sections.
S Yates: So with that background is terms of what we can learn about nuclear by elastic neutron scattering. I'd like to move on and talk about the beta decay and tumble beta decay.
S Yates: I think everybody's familiar with this plot or we have the binding energy or the masses for this case the math 76 hi some bars.
S Yates: And we know that there's a parabola described even members of that would equal 76 is the bars and the odd ones. And of course,
S Yates: positron. The electron capture decay can occur from this side beta decay beta minus 10 K from the other side.
S Yates: And so we get if we have rubidium 76 it's going to undergo positron electron capture indicator Krypton 76 which would indicate to roaming 76
S Yates: The energy here probably restricts us to just electron capture and then you can have bromine 7060 came to the most stable or the mass 76 is of our selenium 76 the other side you can get beta decay of zinc 76 to gallium 76 which would became germanium 76
S Yates: And then there's a problem because obviously germanium 76 is not going to decay to arsenic some six energetically. It's just not allowed. So that process will not occur.
S Yates: So what can occur in order to get to Selenium 76 most stable April 76 is of ours. Well, that's the double beta decay process and the Q value is shown here. We mentioned that in just a just a couple of minutes.
S Yates: And this will be the reaction that is occurring germanium 76 became a Selenium 76 with a nation of to betas and to anti neutrinos.
S Yates: And the question has been asked, could this also occur with the emission of note and the neutrinos. This is a so called neutrino stumble beta decay. This is a hypothetical process. The first of these processes have been observed second has not enough. The second one could be observed.
S Yates: Then we can ask the question, or the answer the question, is the nutrients. Oh man, the particle and we will also be able to determine healthy massive the neutrino. So it's a very interesting process. And there's been a lot of activity in searching through this process.
S Yates: Now the experimental signature when the training was double beta decay is shown here.
S Yates: And if the Q value is. It says here 2039 K GV and the
S Yates: Full
S Yates: Value is shown here is one on the scale.
S Yates: Then we would find that the two neutrino process would give rise to this large blue curve and the neutrinos process will be given by this small red peak here.
S Yates: Now this assumes that the branching ratio is 1000 to one, we know it's not that probably that favorable. So the peak here is going to be even smaller.
S Yates: And so this is then the what we're up against and looking for nutrients double beta decay. The tune internal process is going to dominate and the
S Yates: Neutrinos process is going to be much smaller. And there is one report in the literature, some number of years ago. It's generally discredited now of the identification of this and you can see the data that were used to identify a system, a peek at the right energy
S Yates: But
S Yates: That is not observed, and I think the limits. Now, make it the point so
S Yates: That was not a valid observation.
S Yates: Okay. So where does that leave us in terms of the nuclear structure. Well, germanium 76 is shown here. Selenium 76 is shown there and
S Yates: They are of course apparent in the daughter of the double baby decay process. The two neutrino process. I mentioned it's described here in a very nice nice picture.
S Yates: The half life. This is the most recent value. I found it may be something that's more recent but
S Yates: I'm not aware of it. But you see that the value is on the orange and the 21st years you see the uncertainty in the measurement is less than 5% which means it's been observed in many cases.
S Yates: The neutrinos process, shown here has a limit of greater than eight times 10 to the 25th years. So there's a factor of 20 40,000 or so between these two numbers.
S Yates: Are, of course, two very large searches for neutrinos double beta decay and germanium 76 there's a Meijer on a demonstrator project in the United States Air to project in
S Yates: Europe, the ground so so and
S Yates: You can see that they're fairly similar. And I'm as I understand, they will be joining forces to the next bigger version of the tree last double way deduct a search and germanium 76 which will go been
S Yates: Acronym legend.
S Yates: Now for the paint indicating neutrinos novel baby became process, the decay rate is given simplistically by this equation. And there's a face face factor which I'm told is fairly calculable
S Yates: There's a
S Yates: My around neutrino mass, which of course we would like to determine if we can determine the other
S Yates: Component of this equation, which is a nuclear matrix element and unfortunately we can't measure that nuclear matrix element, we have to determine nuclear structure theory. And therein lies particular problem, because there are various calculation. So the nuclear matrix elements for
S Yates: Treatments double beta decay candidates and you can see this from a recent review paper.
S Yates: And you can see that there are 10 candidates for neutrinos double beta decay. You can see that there are a number of calculations that are listed here.
S Yates: Kwanzaa particle ARP EA interacting bones on model show model, so forth. And you can see that there are a range of values for each of the
S Yates: And they don't really particularly well in the case of the house 76 and train. Let's double waiting. Okay.
S Yates: You can see that they different by more than a factor to and recall this matrix elements squared in that rate equation. So the question is, how are we going to train them, and there have been various approaches to trying to illustrate those matrix elements.
S Yates: people looked at the
S Yates: Occupancy is a single particle estates and such things. We have
S Yates: Studied germanium 76 in selenium 76
S Yates: They of course are the parent and the daughter for the bumblebee decay.
S Yates: They're also structurally, very interesting.
S Yates: Because in this region, we know we have shaped transition
S Yates: Shaped coexistence, I'll talk about a little bit later.
S Yates: There's a question of try XE ality whether it's software region. There are some show closures. There are a lot of things happening in this particular region.
S Yates: And this is a
S Yates: Set of calculations by soaking the moron his colleagues and you can see that they have looked at the structural evolution of the Romanians lean nuclei.
S Yates: The stable germanium nuclei are the ones that are shown in yellow. And you can see that in going from germanium 70 which is
S Yates: Let's see, I should point out the values on this end, the access indicator. We're talking about pro late defamation values on this access home late defamation. You can see that uranium seven is expected to be home late by the time we get to germanium 76 years but it's expected to be probably
S Yates: Similarly, for the selenium nuclei. Again, the stable ones are shown in yellow going from selenium 74 which appears to be all blade to Selenium 82 which appeared to be probably with some indication of tracks ality and other things happening.
S Yates: It's pretty clear that the listen need is a complex complex region, and specifically if you just look at the nutrients double baby DK parent and daughter, you would see them going from germanium 76 which is predicted to be pro late to germanium to Selenium 76 which is predicted to be
S Yates: Either all blade war looks like it has some spherical minimum also doesn't look like a particularly easy transition. And so we're going to be challenged or say theorists are going to be challenging making these calculations.
S Yates: Okay.
S Yates: So, as I indicated, we have done measurements on germanium 76 and this is our paper from three years ago.
S Yates: And you can see that the experiment data for the ground band and the gamma ban shown here, then what's the arrows are proportional to the be tues and you can see that from these to show model calculation to give interactions by Alex Brown, the agreement is fairly
S Yates: Selenium 76
S Yates: You can see also that we have measured experimentally. A number of transition rates. Those are compared with the theory that I mentioned earlier.
S Yates: And you can see that also the, the agreement is fairly good. There are some some problems here and there but nonetheless the descriptions look pretty good.
S Yates: I do want to mention one thing
S Yates: And this arose first one we started looking into medium 76 because we looked at our data and combine that with the data from the literature, instead of data and we got the following set of levels.
S Yates: When Alex rounded his show mala calculations. He got these levels. And the surprising thing is that there are more experimentally known levels and theoretically calculated
S Yates: Usually you would expect it to be just the opposite and expect experimentally missing levels.
S Yates: And so what we had to do is go through and assess whether all of those levels were existing levels or not. And we have a number of levels, which I call erroneous states and these are levels that simply do not exist. So we have to remove them.
S Yates: Okay, then we can do a comparison of the
S Yates: Germanium 76 data and the calculations and of course occur.
S Yates: Now I have to
S Yates: Going to stop and do a little philosophy here because in characterizing nuclear structure where sometimes like the blindfolded scientists who are
S Yates: Trying to determine what an alpha looks like. And you can see that the depends on what part of the elements are examining whether it looks like a fan or spirits naked tree or or or a wall and
S Yates: If someone like that when we're doing measurements because frequently we do management towards particular method or we get particular set of data.
S Yates: And we tend to interpret things in terms of that set of data, whether it's transfer reaction expectation light iron scattering fusion evaporation reactions beta decay.
S Yates: Or photon scattering. We tend to emphasize what we learned from our measurements, but most of these are selecting processes and we don't really look at everything involved. We really want to take a more comprehensive approach. And that's what we've tried to do
S Yates: Because as I introduced it we the inelastic neutron scattering does populate stinks. It's not a selective process. It's critical process, as far as we can determine
S Yates: And so our approaches that we would like to identify all of the excited states up to some energy, usually about three and maybe should be plenty
S Yates: And as many nuclear region as possible, but certainly those near the nucleus of interest. Secondly, we certainly want to eliminate erroneous states.
S Yates: Those states do not exist. And so they shouldn't be considered, we'd like to characterize all of the remaining seats completely by that I mean we would like to identify the spin the parody. The lifetime branching ratios transition rates everything by
S Yates: We're not going to be able to to measure chief actors or or some other properties, but we'd like to characterize the states as fully as possible.
S Yates: We'd like to then compare these data with model calculations and establish some criteria for success of the the calculations and finally
S Yates: I certainly want to retire before anyone can seriously question everything we've done when we think we're being realistic in our, in our assessments and I am not announcing my retirement.
S Yates: Okay, so if we'd like to study other nuclei in the region, where are we going to look. Well, we probably begin with germanium 74
S Yates: Or some good reasons. First of all, it's closest to germanium 76 so also the most abundant of the germanium nuclei.
S Yates: But it has the advantage that the adjacent to it, germanium 73 and odd mass nucleus. This means that we can do single nuclear transfer reactions into germanium 74 and we can do in gamma neutron capture, which is of course a lot of information so we
S Yates: Began our studies of germanium 74
S Yates: And I show first this spectrum. It's gamma ray spectrum. It's made sure to three MTV neutron energy, the annual show, but I want to emphasize the scattering sample used in this case with 19.34 grams of 98.9% and much remaining some
S Yates: Some very favorable situation.
S Yates: Once again, we looked at the number of the states or were provided
S Yates: By the data and the theory. The theory on this calculation, where the calculations of comics brown and we could identify a number of states or erroneous get rid of them states, then our comparison between theory and the calculation is really good.
S Yates: And again, these are the erroneous states we got rid of
S Yates: So if we compare them.
S Yates: Calculations
S Yates: With the experiment. These are show Mon calculation by Alex brown. You can see that the energies are quite
S Yates: Not surprising.
S Yates: But I should point out that Alex provided us the calculations several months before we had completed our announced. So the data.
S Yates: And I asked, Alex, if he wanted to see our data tsunami was available. And he said, no surprise me. So I had an opportunity to visit Michigan State last spring in a seminar.
S Yates: And I surprised, Alex. Because the thing that we really like to see is how good are the transition rates in comparison to the calculation.
S Yates: And this shows a number of transition rates as well as our chemical comparison with our calculation with Alex's calculations.
S Yates: In each box you'll see that there are two numbers. The first number with an uncertainty is the experimental value and vice golf units.
S Yates: And the second one is the calculation. And you can see that the agreement is really spectacular. I was really shocked that it was this good
S Yates: And I want to emphasize that Alex has adjusted nothing here except for, I think that the be to the first two people, a state to the ground state. So,
S Yates: You're, you're very, very well received. You see that even for the mix symmetry state, the agreement of very good
S Yates: So this zero plus band. I'll say something about later. But we're really very pleased when we saw these results. This means that the show mana calculations are doing a good job in this region.
S Yates: So if I were asked to evaluate the status of germanium 74 we believe all states below two and a half and maybe an identified it may be that we
S Yates: Go up to 2.8 MTV or so you don't really know we've eliminated. Many erroneous states the lifetime of one state below 2.8 MTV was not measured who can only establish a limit for that lifetime.
S Yates: Similarly, there was only one state below 2.8 MTV that we could not definitely assign us in parenting.
S Yates: And the agreement with the show can show mom calculations, as I indicated, I really describe it so spectacular.
S Yates: So where does that leave us. Well, there are a number of challenges and opportunities, of course.
S Yates: We're waiting the discovery of neutrinos double beta decay. This is, of course, if it is discovered, it's going to be a fantastic event.
S Yates: If it is observed many nuclei should be studied to understand the nuclear structure in the region because the better we can calculate the
S Yates: nuclear matrix elements of course a better value for the neutrino mass and additional experimental method should be employed and of course the calculations will be improved also
S Yates: Now I should also point out that these are Romanian is not the only place we measure properties of nutrients double beta decay candidates.
S Yates: This is a complete listing of those we have examined in our laboratory. See, they go from calcium 48 some years ago to a new 150 which is in progress.
S Yates: You can see that the they're shown generally in Paris with the parent in the daughter of the same color. And so we can do a number of studies and provide this kind of information to hopefully constrain the calculations.
S Yates: Okay, so with that in mind, I do want to say one final thing about the structure germanium isotopes. And this has to do with shape coexistence now shape coexistence in this mass region has been known for almost 50 years
S Yates: Joe Hamilton and his colleagues and identified shape coexistence in selenium 72 and 1972 and shape coexistence is usually Vince by
S Yates: Law line zero plus states and these states have different different shape than the ground state, and the one that of course attracted a lot of attention is of course the first excited state of 72
S Yates: One of the few even even nuclei that has a first excited state that's not two plus and so
S Yates: This picture of shape coexistence who's described and particularly the review article by Chris hide and john one
S Yates: And I don't want to go into detail what this diagram with the top of the page shows, but I want to point out that shape coexistence in the germanium isotope
S Yates: Was identified and characterized almost exclusively through transfer reactions. And so in this picture. If you have horizontal lines. These indicate the two neutron transfer reactions vertical lines indicate the two proton react transfer reactions and I get aligned indicate alpha particle
S Yates: Reactions and some of those reactions are shown here and
S Yates: In their review paper john and Chris made the comment that the the transfer reaction spectroscopy in its details and unequaled anywhere else on the nuclear surface. And so we asked the question, well, we shouldn't be able to see now the gamma rays of characterize
S Yates: characterize these
S Yates: Collecting the structures built on the zero plus states. And so we look into the literature and this is what we found. We found some evidence in germanium 68
S Yates: Have a large be too and recent cool excitation data, your medium so many too, but we didn't really find anything else we would say characterizing it's characterized as collective expectations of we would expect.
S Yates: Will change for existing structures.
S Yates: So we add in what we had contributed and what I showed you in your menu 74 and you can see that we now have a two plus and a fourth bus and this looks like the kind of band structure that we expect
S Yates: Or shape coexisting man again. I call this preliminary because we we haven't published it. I think the numbers are pretty good.
S Yates: And then the question arose. Well, what about germanium 76 because we studying during my name 76 in detail. We didn't identify any kind of a collective expectation or collective level built on top of the civil plus they did we just miss it.
S Yates: Well, we can look at where the next excited to plus state will be, it should be a 500 K 93 K be above the state.
S Yates: And so we went back to our data that we've taken several years ago from the Indian Prime gamma reaction on germanium 76 and
S Yates: Interestingly enough,
S Yates: When we saw them all of our data three me, we were able to see a small peak right and exactly the right energy
S Yates: We looked at the excitation function for that peak. You can see it extrapolates quite nicely down to 2.5 MTV.
S Yates: And we, in our measurement or previous measurement had measured the lifetime that level there's a fairly large and certainly
S Yates: Where we can then extract be to 21 vice coffin.
S Yates: So if we go back to our picture, but that in number in. Now we're getting something, it looks like we're able to see the
S Yates: Shape coexistence picture a little bit better. And then germanium 72. We've also measured this transition our values, a little bit different from the cool x value. But nonetheless, you can see that indicates that this is collecting
S Yates: And maybe even more information available. It wasn't accepted by the nuclear data sheets or the end staff compilation, but may well be that valuable this transition also. So the picture of shape coexistence in germanium nuclei. My electromagnetic case is becoming a light color.
S Yates: Okay, let me close by acknowledging my, my colleagues those at the University of Kentucky Accelerator Laboratory Mark McAllister, my longtime colleague Diane last year.
S Yates: The other contributors, particularly those in red, or the monster contributed most to the engineering remaining 76 mile to the germanium studies in general and of course are calling Alan brown Michigan State University and I would be remiss if I didn't show you what Kentucky looks like.
S Yates: In the spring, obviously, in this picture right maybe more info here and you're all invited to visit, hopefully, on the one at a time. Thank you very much.
James Smallcombe: Thank you very much, Steve.
James Smallcombe: So yes, we'd like to open the floor to questions. So as I said at the start, but you can go to participants many
James Smallcombe: Find yourself the raise hand icon there or if you want to type in the chat box and I'll read your questions out
James Smallcombe: So while they started. So, after having motors panic. Steve, you said you're not retiring. Yeah. So what are your, what are you got your sights set on next.
S Yates: Well, of course, we'd like to finish the uranium nuclei and then move on to the selenium.
S Yates: It takes a fairly massive effort to finish one of these sets of measurements, but it doesn't mean that we look forward to doing them.
S Yates: The
S Yates: The selenium nuclei. I didn't mention that specifically, but a shell Mon calculation that Alex did in selenium 76 are not quite as impressive as those in germanium 76
S Yates: And so we'd like to try to determine exactly what is happening in the joints pulling a little bit better but you can't do everything on day one.
James Smallcombe: Yeah yeah no good work just
James Smallcombe: I'm very interested in selenium. So maybe, yeah, maybe don't get there just yet. I've got some work to publish first
James Smallcombe: So we've got some questions lined up now. It's great. So, Rudy, I think you were first going to go ahead
Rolf-Dietmar Herzberg: I stay. Thank you very much for that beautiful talk and was very, very interesting. Now one of the things I can you hear me.
S Yates: Yes, I can.
Rolf-Dietmar Herzberg: Okay, good. Sorry. One of the things I learned about double beta decay is that the odd one. In between the two is also interesting because your decay can go via virtual expectations of those states. Now, the
Rolf-Dietmar Herzberg: Arsenic 76 only has a half life of a day, which I suspect is twofold for you. What is the lower limit for the half life before you can contemplate getting a large enough sample to do something with it.
S Yates: You asked a very complex question, Rudy, because
S Yates: Of course you would like a large amount of material and as the half life gets shorter the radiation levels increase
S Yates: And so typically, I would say that we need 10s of years in order to to have something that's have an acceptable half life for us to have a lot enough material for our measurements.
S Yates: That's not very encouraging. Yes.
Rolf-Dietmar Herzberg: Well, not for the arsenic case, but I haven't had the chance to look up all the other ones in between, which you probably have done.
Rolf-Dietmar Herzberg: So is there any any reasonable chance because hardly any other method is able to do this complete spectroscopy that you can do with a neutron. So it's a it's a very, very brilliant tool for that kind of thing.
S Yates: Oh, thank you for your analysis of our work.
But
S Yates: Yeah, it is very difficult, and we in fact
S Yates: Have done an experiment at the end you to look at
S Yates: The arsenic 76
S Yates: It's
S Yates: As you mentioned, it's an odd on nucleus of the level density increases very rapidly. It's very complex.
Rolf-Dietmar Herzberg: Okay, thank you.
James Smallcombe: Great. I think Kelly was next to me. Go ahead.
Kelly Chipps: Hey, good morning, Steve.
Kelly Chipps: So speaking of the show model calculations and this might be a better question for Alex, but perhaps you can speak to it what what is this particular interaction, like I'm not familiar with this J un 45
Kelly Chipps: Interactions, it is it well constrained in this mass region.
S Yates: I'm actually the best thing I can do is recommend that you go to the appendix of our selenium 76 paper because Alex has gone through and explain exactly what his interactions are
S Yates: That's, that's, that's the best I can offer
S Yates: But
S Yates: One. One of the things that I certainly learned in working with
S Yates: Working with Alex is that he will tell you if things don't work. And if he doesn't understand things
S Yates: And oh,
S Yates: I think that's the best I can tell you a simply look at the selenium 76 paper he describes how he labels. His interactions. And that's, that's, I say is the best reference
Kelly Chipps: Okay, thanks.
James Smallcombe: Okay, we've got another question from Marcus.
Marcus Scheck: Hi, Steve.
S Yates: Hi modules.
Marcus Scheck: From this large number of states they to do a bit of Sherlock hates look where they are all coming from. Could you narrow them down the messages or
S Yates: Yeah, and and this is unfortunate because
S Yates: One of the things that frequently see is that
S Yates: These erroneous states are often state.
S Yates: transfer reaction, some years ago.
S Yates: And so if you have a contaminant
S Yates: Target.
S Yates: From that target material. And so it gets into the literature and it gets into the evaluations and the evaluators are low to really
S Yates: Eliminate states. Now this has led us to in our most recent papers on germanium 76 and selenium 76 and in our future papers to go through a list of states that we believe are incorrectly placed so that maybe they'll be taken out of the literature.
S Yates: That answer your question mark.
Marcus Scheck: Yes, mostly the pot or transfer thought
S Yates: Okay, well,
S Yates: It's it's a difficult thing and I know I understand why evaluators don't like to eliminate states, but I think that we must be going in that direction because it's important thing is one is right.
Marcus Scheck: I completely agree. We were suffering with supposedly sea level in 96 molybdenum, which is not there.
Marcus Scheck: You
are welcome.
Philip Adsley: Hello and thanks very much for that talk. I, I enjoyed the fictional levels bit. And the reason that I was doing something similar with protons with the key 3D
Philip Adsley: Munich. And I was wondering. On a related note, how high in energy. You can go with excitation with the neutrons, because I've seen this problem in, for example, neon 22 up gamma this as a couple of levels, seeing from our transfer reactions on neon 22 ourselves that just appear to be fictional
Philip Adsley: And don't air and any other reaction. I was wondering, but they're at like nine MTV. Is that a bit too far.
S Yates: Well,
S Yates: For us, we'd have to use a different reaction, rather than 20 reaction on tritium we could use the end reaction. And that gives it will get us up to about 9am a B.
S Yates: Or you could use the DT reaction. So you've got a variety of reactions that will give you a neutrons. And so if if you have a specific problem.
S Yates: Let me know. And we can see what we might be able to do
Philip Adsley: Okay, that's great. Thanks.
James Smallcombe: Excellent.
James Smallcombe: Do we have any other questions. So a few hands that disappeared. So I guess the question to be answered.
James Smallcombe: If you don't have the raise hand function, you are welcome to unmute yourself and go ahead with your question.
James Smallcombe: I don't see anything in the chat box.
James Smallcombe: Now, I don't see anything. So in my case, I think we'll call it that, and say thank you very much. Steve for a great talk on some very impressive work you've got going on over there. Thank you for taking the time to speak to us about it.
James Smallcombe: And a pleasure. And thank you, all of you for joining us for another one of our lockdown on social distancing seminars.
James Smallcombe: As I mentioned at the start, we will not have seminar next Monday as it's a holiday here in the UK, but we do have this Wednesday we have a student warfare from student taught channel which is Simone.
James Smallcombe: Regarding sorry if I got that wrong from the University of bonus of Birmingham talking about the UPC in Alice a wonderful microscope for one PDF
James Smallcombe: So come along and check that out. And we'll see you back here for another one of our talks in two weeks time. So thank you very much. Steve, thank you very much audience and have a very good week. Bye for now.