James Smallcombe: And I will hand over to Alex so please tell us about your work.
Alex Gade: Okay, thank you very much for this introduction it's really a nice opportunity to speak a little bit about my research during the pandemic.
Alex Gade: we're all conference travel was essentially non existing i'm sorry so it's actually morning here and there's no outside so it's probably very different from your place.
Alex Gade: So what I wanted to tell you a little bit about first, is where the experiments that I will be presenting have been performed and that's.
Alex Gade: At the national superconducting Cyclotron de Barra Tory at Michigan State University and we are also hosting on the effort laboratory at present and we have more than 600 employees and.
Alex Gade: More than 40 of them are faculty members across experiments theory and accelerator physics and chemistry, and we have more than 100 graduate students and 60 undergraduate students.
Alex Gade: And so i'm at present we are funded to run.
Alex Gade: The nsc me as a user facility for right so for the isotope research and education and i'm soon effort will become operational, and we are present in the moment.
Alex Gade: We are in the process in we are, we are transitioning into effort, right now, and if you haven't been at the laboratory recently and you might not recognize us and.
Alex Gade: This is how the front face of nsc a look like in 2003 and then every six to five years we seem to be adding office buildings to accommodate all of all of our researchers and engineers.
Alex Gade: So we are actually located right in the middle of the Michigan state university campus, this is the front face I I showed you before this those are the office buildings.
Alex Gade: And this is where all the experimental equipment and the beam lines of the President and seo facility located and what you see here, those are buildings that actually look quite new This is where the linear accelerator of effort.
Alex Gade: is actually being completed and is commissioned at the moment and it's indeed folded like a paperclip, and this is the target area so effort is a fragmentation facility and then the fragment separator will bend into the existing facility so that we can use all of the beam lines.
Alex Gade: And you see here across the street, we have plant biology, we have biology physics, chemistry, the law school and performing arts, so we are right in the middle of a campus with.
Alex Gade: Such an exciting facility so i'm the menu I prepared for you today is I first wanted to give you a little bit of a big picture introduction of the science themes we are interested in and how.
Alex Gade: The particular approach that i'm interested in in being gamma Ray spectroscopy fits into this and then i'll just briefly remind you a little bit of.
Alex Gade: The battle of Resolution versus efficiency and the sort of the science which kind of array we use for our nba gamma Ray spectroscopy.
Alex Gade: So i'll only pick three science examples and they're all related to nuclear structure, research and tracking the Shell and shape evolution at neutral number in equal to 40 and then how to use.
Alex Gade: emory tech direct reactions is extremely selective tools for spectroscopy and then little bit about.
Alex Gade: Competing configurations that we found inside for 43 and all of these results were from the past 12 months and typically our research can be all across the nuclear chart and, but we are confining myself sort of to medium heavy nuclear.
Alex Gade: um so if i'm thinking about the seams of of rare isotope science at nsc and you can reframe this and that's probably true for all the facilities we're interested in the properties of nuclei and the goal is.
Alex Gade: To develop a predictive model of nuclear and their interactions and we're always interested in what are the limits of the elements and the isotopes.
Alex Gade: In terms of contributing to astrophysics nuclear physics, is very important to figure out the origin of the elements in the universe, or to characterize explosive environments, such as Nova supernova X Ray bursts.
Alex Gade: Or the properties of neutron stars.
Alex Gade: And test a fundamental symmetry some nuclei on have symmetry or have effects of symmetry violations amplified so they are very interesting laboratories to search for physics beyond the standard model and, for me, the study of week interactions.
Alex Gade: Also, is part of studying fundamental symmetries and then in terms of societal applications there's not just includes medicine biology and environmental and material science, but in the US also national security.
Alex Gade: So how do we fit into this, if you think about gamma Ray detection devices, you see a picture of Christina and the picture of a scintillating array that's called Caesar.
Alex Gade: And of course the properties of nuclei what the often do is we use direct reactions that use gamma Ray tagging to identify excited states or we can determine excited state lifetimes by using.
Alex Gade: very advanced doppler techniques, for example, for nuclear astrophysics and very often.
Alex Gade: Huge gains in constraining reaction rates can be achieved by measuring very precisely the energy of excited states and also their properties, for example, spectroscopic factors, and this can really constrain P gamma capture rates for the rfp process, for example.
Alex Gade: um.
Alex Gade: We have a quite active program that uses charge exchange reactions gamma Ray text ones to pro week interactions.
Alex Gade: And then of in terms of societal applications those studies of reactions that can be surrogates for neutron capture reactions, for example, and they can be gamma Ray text and their application can be in react or science or national security, for example.
Alex Gade: And for all of this, I like to think that in game gamma Ray spectroscopy can play a role.
Alex Gade: So i'm for all the examples i'm going to show you the experimental scheme is is always roughly the same, and this is shown here what you see here is.
Alex Gade: The freshman separator in 1900s of the nsc, so this is just a transport beam line, and this is the beam line that leads to the SI 200 spectrograph and you see here, this is sort of a vertically.
Alex Gade: installed separator so our real I saw two beams are produced by fragmentation not seen on this slide is our driver accelerator, which used to be the couple Cyclotron facility providing beams of say 150 MEP perfectly on off of stable beams and then.
Alex Gade: Through fragmentation at the entrance of the freshman separate a whole issue of fragmentation residues is produced and then separated out.
Alex Gade: In the Franklin separator using iron optics and register and slits and then the isotopes of interest and they often come in the cocktail being.
Alex Gade: transported to the SI hundred spectrometer beam line shown me and this be mine has a target position.
Alex Gade: As indicated here, where we like to put our detection array so we take those were isotope beams inducer reaction gamma Ray spectroscopy tells us what the final status that was populated.
Alex Gade: And all reaction residues to project I like ones are being event by event identified in the fragments separator us in the spectrometer part using energy loss and time of light and all the observable that are used for this.
Alex Gade: So the example is i'm going to show you i'm used either Christina or CESAR.
Alex Gade: So, in terms of Christina i'm suspecting that you had.
Alex Gade: Several talks, maybe from from people that do experiments with agata or that perform experiments with cuttino so i'll be.
Alex Gade: very brief and Christina at the moment, consists of 12 detector modules each detector module holds for Christmas and they are shown here they have slightly different geometries called A and B and each of those crystals is 36 fold segmented as shown in this.
Alex Gade: sketch, right here, and then.
Alex Gade: For each detector for each crystal we read out 40 electronics channels, this is 36 segments, and the core signal is.
Alex Gade: A read out at four different energy ranges so then i'm the waveforms that are being taken from from all these segments, they are they digitize that hundred megahertz 14 bit digitize us 200 megabytes per second of throughput.
Alex Gade: And so we have four digitize us per per Crystal and so Christina is actually moving between facilities, and so we.
Alex Gade: So we it travels with with a heavy baggage and it comes with this digitize our farm in addition.
Alex Gade: We perform signal decomposition so it's not just comes with thousands of electronics channels, it also comes with its own computer farm.
Alex Gade: As indicated here so signal decomposition of all the waveforms is performed to determine interaction points of the gamma rays inside all of the different crystals, and so what we get at the end of the day, for each.
Alex Gade: event is an energy an X, Y Z coordinate inside the detector and the time signal so roughly we get the energy split and the location of Cameron interactions.
Alex Gade: And so, let me tell you why we need this.
Alex Gade: When I explained to you the experimental scheme, you will have realized that the gamma rays that are being emitted at the target position of the asset hundreds.
Alex Gade: spectrograph there will be emitted at very high velocities and those velocities are about 40% of the speed of light so in the laboratory frame if we just.
Alex Gade: Take all of the gamma rays in reaction as they, as they are being detected in the Left frame this is from some older work we did on titanium 60, this is the very unspectacular bump you can detect and then, if we take just the doppler reconstruction equation, we.
Alex Gade: Put in the velocity which we know things to the spectrometer and the emission angle, which we know, because we have X, Y and Z for each gamma Ray interaction point and we get this and the bump is transformed into a transition.
Alex Gade: And the energy resolution is so good that we can actually see that this transition is not just one peak but two peaks.
Alex Gade: So um I told you, one of the examples uses a different detection array and this detection array is called Caesar and what we're doing is.
Alex Gade: For some experiments, we can afford to trade efficiency are for resolution so Cindy later arrays, as you can see from this picture here and they are very they can be very densely packed.
Alex Gade: And so.
Alex Gade: This is the beam pipe here and the spectrograph would be behind this magnetic shield right here, and the target would be somewhere in the middle of the Caesar right, so this beast was commissioned in 2009 and is often used around the target position.
Alex Gade: At the S 800 but sometimes we also.
Alex Gade: collaborators also use it together was charged particle arrays, for example, to study in flight proton emission and Caesar then would look at the gamma Ray the case in the proton emission residues or it has been used quite a bit now for.
Alex Gade: invariant mass spectrometry using neutron detection.
Alex Gade: With the modular neutron array, and this we permit so i'm the thing has 192 high grade cesium iodized sodium metal detectors and the solid angle coverage, as you can guess from from this dense packing is more than 95% and the test quite high.
Alex Gade: Efficiency at at one me be 35%, and this includes epic routines where i'm from adding back neighboring Christmas we can reconstruct scattered gamma Ray events, so the resolution is.
Alex Gade: 9% in beam, which is a very different from Christina, and this is how it looks like.
Alex Gade: From a recent example by one of my former radio students who took a look at experiments at the proton drip line and you see if the level density is not very high, one can perform.
Alex Gade: very nice spectroscopy and for for high energy gamma rays, because of the high efficiency, one can, for example, is done here exclude certain branches that were proposed in the past.
Alex Gade: So um but the first two examples i'm going to show you um they did use Christina and Christina can be used.
Alex Gade: At the asset hundred spectrograph beam line in different configurations here, you see a side view the real isotope teams come barreling down these beam line here.
Alex Gade: The reaction target is in the middle and patina detects the gamma rays limited in flight the reaction residues grow up in the spectrograph focal plane, the standard configuration is we pack as much as possible and the for what angles.
Alex Gade: um as shown here or the detector modules we have one configuration, where we pack all detectors in one hemisphere and then we can accommodate the liquid hydrogen target, which is cryogenic and it comes with a lot of stuff attached.
Alex Gade: And we have run configurations where we put everything in one hemisphere and the other side is covered by neutron detectors.
Alex Gade: He has shown the lender array and we have very fancy target systems, namely plunger devices and here's a picture of the triple plunger designed and often used by your iwasaki.
Alex Gade: So i'm so far over the life of the nsc air, which is coming to an end in a year or so um we have performed three Experimental campaigns and Tina has been traveling between an acl and argonne national laboratories and we have performed 62 experiments if I counted right.
Alex Gade: And, in general, the interest was to study collectivity, for example, column excitation or a tracking chip changes.
Alex Gade: In islands of inversion or n equal to Z or along I saw topic change using electromagnetic transition rates to benchmark theory.
Alex Gade: Another topic of interest is nuclear astrophysics as indicated before very precise energy measurements of of proton capture resonances are important for the rfp process angle integrated.
Alex Gade: Transfer reactions can be used to also determined spectroscopic factors sometimes neuro symmetry is used to constrain proton capture rates and we have a program that uses chance exchange reactions gamma Ray text wants.
Alex Gade: to study electron capture rates which are important for corporate web supernova i'm not picking any astrophysics examples, and I want to refer to.
Alex Gade: You to given Lotus talk this Friday actually hosted by gina you see the website here, where you can sign up and i'm sure given includes in his talk one of his recent uses of Christina at an seo.
Alex Gade: i'm surely evolution somewhat related to studying collectivity one uses or one tracks, the single particle degree of freedom.
Alex Gade: In islands of inversion along I saw topic chains, for example, or one is interested in core excitations and props.
Alex Gade: Nuclear models in that way, we also always have some been time for developments, the commissioning beam time resulted in tuning papers on we have.
Alex Gade: We are analyzing data right now that will give us the absolute gamma Ray efficiency of cortina in beam at six MTV and we have even given a beam and experiments to some schools.
Alex Gade: So the examples i'm going to show you only three of them.
Alex Gade: The first one is related to nuclear structure physics and tracking the Shell and shape evolution towards neutral number n equal to 40 in the chromium isotopic chain, the second run and i'll take you to the proton reply, namely to scan the 40 and they'll show you.
Alex Gade: How we stumbled across a very unusual very small cross section reaction that turned out to be really, really selective.
Alex Gade: And then, at the end i'll show you what we have done with CESAR recently in studying sulfur 43.
Alex Gade: Which is of relevance for the N equals 28 island of intuition so i'm.
Alex Gade: chromium 62 and 64 where the topic of one of our recent papers and i'm already.
Alex Gade: Thinking all of my collaborators, which are listed here um, and so the motivation is.
Alex Gade: For me on 64 turned out to be really hard to reach this first spectroscopy was done 10 years ago.
Alex Gade: entered actually validated extremely precise predictions, which were done by Sylvia threaded Plato and Camilla and i'm showing you this reference here we're on an island of inversion around chromium 64 is characterized.
Alex Gade: And i'm so this theory paper and our experimental work came out except essentially at the same time, and so the predictions or the calculations provided in this paper, they were really predictions, because they had no way of knowing our energies.
Alex Gade: And the first two plus energy and the ratio of the four plus and two plus energies for chromium 64 they were almost right on the calculation so that's extremely impressive.
Alex Gade: And also, of course, islands of inversion we learned a lot about surely evolution and the drivers of of changes in the nucleus, which is structure so reaching chromium 64.
Alex Gade: Is kind of interesting, and so this this happened 10 years ago, this was inelastic scattering and we use the sega array for gamma Ray detection It took three years to look at chromium 64 again, this is the coolest excitation.
Alex Gade: experiment or the spectrum of that, and this is the first two plus date as cool i'm excited and and the detection was done with the Caesar array I showed you, and then it took one more year for.
Alex Gade: Somebody to look at the beta decay of Canadian 64 and find a peek at about the right energy here, as you see.
Alex Gade: So um what our motivation was we wanted to learn about excited states beyond the first two plus and four plus Okay, if this nucleus is at the heart of this n equal to 40 island open version we want to know more than just two plus and four plus energies or the tubing.
Alex Gade: and also this configuration and shape coexistence.
Alex Gade: commonly observed in islands of inversion magnesium 32, for example, or sulfur 44 in the N equals 20 and 28 islands of inversion and what's the deal at n equal to 40 so we found this interesting to look at and then.
Alex Gade: This effective interaction I showed you the paper for is also basis for an extrapolation towards the end equal to 50 island often version which is centered around Nicole 78 so probing what this interaction does at n equal to 40 is useful for extrapolations.
Alex Gade: So the experiment, we performed now what is it one and a half years ago, maybe two years ago.
Alex Gade: With patina at the sh hundred used to cocktail beam of rare isotopes manganese 6566 cobalt 68 on a brilliant target and we looked at the reaction visit us.
Alex Gade: And so, chromium 64 was produced in different ways from manganese 65 and from Ireland and kobo then we couldn't tell which project I would use it.
Alex Gade: And what you see is, indeed, for the first time, we saw one more demaree than previously observed, and you can already see there's maybe much more going on.
Alex Gade: For free I should show you in here that's the advantage of a large acceptance spectrometer you're not just get your nucleus of interest you get this best friends.
Alex Gade: And chromium 62 came for free, and so we could do the same for chromium 62 which had about the same level of knowledge in terms of excited states and to also we see.
Alex Gade: The third gamma Ray transition and more stuff at higher energy and i'm the first notion, we had was where those spectrum of really similar.
Alex Gade: And yet we have seen three strong gamma rays in both chromium isotopes, but if we zoom in, and this is the region like behind.
Alex Gade: This third gamma Ray there are actually many more transitions and they are all week, and if you know about building level schemes, they will make your life really miserable.
Alex Gade: So can we learn something about coincidences from chromium 64 So what we will be take a look at gamma rays that come in time coincidence.
Alex Gade: Here, what you see here is a matrix plotted is energy of one gamma Ray versus the energy of the of the other gamma Ray if therefore fulfill a coincidence condition and those dots here indicate.
Alex Gade: gamma Ray coincidences and one can project, and one can see coincident to the first two plus date.
Alex Gade: Is the transition we claim as to the four plus two, plus transition and maybe we get the third transition back then we can do the same, we can put the gate.
Alex Gade: Software coincidence on the four plus two, plus transition and we get the lower transition back and we seem to get the higher transition back as well.
Alex Gade: And so we were brave and we proposed, well, we found the cascade and we dare to call this 900 whatever gamma Ray i'm tentatively as decay of the six plastic, why can we do this well.
Alex Gade: We go to very nice level scheme from the LM PS shine model effective interaction, where I showed you the reference for on the previous slide and the six plus.
Alex Gade: four plus transition, indeed, is almost within 10 kV of the gamma Ray that we observed Okay, and remember those two transitions were already very precise so we felt kind of good about our assignment here.
Alex Gade: And I should tell you about this level scheme, and these are, of course, the energy levels and transitions but the line width corresponds or scales, with the be of equal value, which we did not measure in this experiment.
Alex Gade: And what you'll see is very interesting structures, built on the.
Alex Gade: Second zero Plus in second two plus states this almost for the old camera spectroscopy this looks like a gamma band, this could be like a beta and so very interesting collective structures.
Alex Gade: That indicate that there might be shape or configuration coexistence going on, that you know this band has a different shape for configuration than those two bands.
Alex Gade: So also this level scheme is kind of messy has lots of transitions and that's maybe exactly what we see with those many week transitions I showed you.
Alex Gade: So now, I thought this is going to be boring, and I just do the same with chromium 62 i'm looking at the coincidences for chromium 62 and you see the matrix already looks different.
Alex Gade: And the third gamma Ray is actually in coincidence, to the first two plus um but not to the four plus two two plus transition, so the only level scheme, I can build with this is like that.
Alex Gade: So that gamma Ray, even though the spectral look very similar doesn't seem to be the six plus four plus transition Okay, so we resort to share model again like we always do when we don't know anymore.
Alex Gade: And we take a look at all the transitions that go to the two plus state and one candidate is this second zero Plus state, which again is predicted to have a very interesting structure collective structure.
Alex Gade: built on top of it okay so um we might have found a candidate for the second zero Plus state.
Alex Gade: So, even though the spectra look very similar well they seem to show different picture of population so.
Alex Gade: If you allow me to to briefly summarize this, and so we provide it, for the first time spectroscopy of excited states and chromium 64 and chromium 62 beyond the first two plus four plus states.
Alex Gade: i'm at least to my surprise me, we found not a candidate for the six plus dating chromium 64 that was not surprising, but chromium 62 looks different.
Alex Gade: And that gamma Ray the third gamma Ray that looks very much like the picture and chromium 64 from its coincidences it's more likely, the second zero Plus state.
Alex Gade: And in working with our theory collaborators and making those levels schemes we.
Alex Gade: found at least for me very exciting predictions for two collective structures that live on top of the second zero Plus state.
Alex Gade: And the second two plus date in those nuclei and they are indicative of exactly what I what I mentioned before, that in those islands of inversion is a lot of shape and configuration coexistence going on.
Alex Gade: So i'm for sure our observations of having those many week transition they sort of fit with this messy picture of having all those competing configurations.
Alex Gade: And for sure, having having those collective bands that might excite high spin physicists again, and they will certainly motivate future experiments.
Alex Gade: So um let me go know to a different region on the nuclear chart for telling you about our finding on very low cross-section reactions that turn out to be.
Alex Gade: Extremely selective, and this is the Indian gamma Ray spectroscopy of scandium 40 and I must say, before I stumbled upon this know players, I didn't know anything about it.
Alex Gade: So this experiment where was focused on learning about calcium 38 first include on excitation and then in fragmentation reactions.
Alex Gade: And when we looked at the particle identification in the US 800 spectrometer and we found scattered calcium 38 we found to neutral knock out all sorts of fragmentation residues, but on top of calcium 38 we found.
Alex Gade: Another block block is a technical term for those structures in particle ID figures and if you if you know how particle ID works, this has to be scandium 40.
Alex Gade: Okay, why is can do 40 so unusual and if you have very fast beams like 60 MTV pro-nuclear Anwar 70% of the speed of light in to think about transfer reaction.
Alex Gade: reactions and we are adding here to calcium 38 we add a neutron enter proton at the same time and.
Alex Gade: And because of the high velocity of the calcium 38 beam and this reaction is extremely momentum mismatched okay so cross sections.
Alex Gade: For such a reaction, have to be very small, and indeed they turned out to be very small.
Alex Gade: So calcium 38 that 60 me be perfectly on about hundred 60 particles per second coming in, on the brilliant target and we get with eight microbiome I have not done microbiome spectroscopy before with eight micro bonds, can you 40s being produced.
Alex Gade: Okay, that doesn't look impressive, this is only a few hours of the data, but we can look at what does patina see.
Alex Gade: In coincidence with scandium 40 and we got this very clean spectrum.
Alex Gade: was to gamma rays 892 and 1800 50 kV and then we started to look into the data sheets and we found that nobody nobody had ever looked at Canyon 40 with gamma Ray spectroscopy.
Alex Gade: Okay, so, and this is, for me, this is mind boggling because i'm showing you here the part of the nuclear chart.
Alex Gade: You see here, calcium 14 diagonally away from scandium 40 so many charge exchange reactions have been done, but none of them ever used to gamma Ray detector ever um but then scandium 39 was shown to be a ground state proton emitter so well.
Alex Gade: i'm scandium 40 is actually a drip line nucleus, even though it's a neighbor of calcium 40.
Alex Gade: So we can look at all the beautiful particle spectroscopy that was done with either gregg Braden spectrometer or.
Alex Gade: A split polls at lower beam energy and we found that this camera 892 is the five minus two four minus transition in scandium for the.
Alex Gade: So the state was known before but looking in the data, nobody has seen a state that corresponds to editing the to gamma rays, and we have some week evidence from coincidences that they are sitting on top of each other.
Alex Gade: So whenever we don't know we resolve to theory or the proton which side we look at the mirror know players Merrill nucleus of scandium 40 is potassium 40.
Alex Gade: And this is what's known from particle spectroscopy four minus ground state the five minus excited state, there are two more states to minus three minus that we don't see this guy below here is a nice warm air and there's two minus we don't seem to populate.
Alex Gade: So we were brave and we put our second gamma Ray on top of the five minus and then, if we compare to the mirror nucleus there to candidates states and i'll tell you why i'm only looking at high spin positive parity States here six and seven, then we resort to share model.
Alex Gade: And they're the same two states, right here, so let me tell you why we believe we actually populate the states that we.
Alex Gade: observe here.
Alex Gade: So I mentioned before, we are at very high beam velocities for potassium for calcium 38.
Alex Gade: and saw the reaction will only ever happen if the proton and neutron are being picked up into high orbital angular momentum.
Alex Gade: States OK, so the configurations we populate is where we put one proton in f7 have you put one proton in these three half, which then leads leaves sort of a hole in there and then we can Couple this to five minus perfect that's exactly the state, we see.
Alex Gade: um what I should also say is that this momentum mismatch leads to the fact that stretched cascades are being populated, so you have to.
Alex Gade: couple it to the highest angular momentum, not to the lowest if you cover this configuration to the lowest angular momentum you get the tiny mistake which we don't populate so that all makes sense.
Alex Gade: So now, if you think about in this scheme of highly mismatched anti orbital angular momentum and stretch cascades we should see.
Alex Gade: proton enough seven half neutron and f7 half copper to what are the two highest six plus seven plus Okay, and those are exactly those two states, I point out to you in the mirror.
Alex Gade: And in the sharing model, so what we assumed or propose is that this.
Alex Gade: state that we saw is one of the two and it's either the six plus or the seven plus and that we did us from the high selectivity of this kind of strange transfer reaction of 8 million of eight microban cross section so then.
Alex Gade: We looked into the proton emission but I didn't tell you is that.
Alex Gade: All of these States here they actually proton unbound proton separation energy is only 530 kV Okay, so this beast this new state, we found is very much above the proton separation energy.
Alex Gade: So Alex brown the proton decay calculations for us and assuming some l equal to four proton emission of this kind of configuration.
Alex Gade: To the ground state of calcium 39 that's, the only way that such a state can decay.
Alex Gade: And it turns out that the seven plus would probably be a very fast proton emitter and the six plus we'll have a gamma Ray branch and that's the branch we see, so we claim this J plus assignment is actually the six plastic.
Alex Gade: This all looks like very beautiful and we have figured it out, but there's one.
Alex Gade: drawback I should tell you the mirror nucleus, as well as sharing model would like to see the six plus decay, to the seven plus and we don't have any evidence for this transition which might mean the seven classes, maybe a little bit of buffer or it's too close.
Alex Gade: For a gamma Ray to be like.
Alex Gade: So why I found this example exciting is maybe because of this small cross section, first we provided the first gamma Ray spectroscopy of scandium 40 ever, even though it has been studied for for 50 years.
Alex Gade: And it's actually proton reply nucleus, and we totally from this reaction channel, by coincidence, we will never looking at scandium 40 it was just one of the blocks in our particle ID.
Alex Gade: And for me surprising, maybe, if you do fast beam spectroscopy were sick targets and there's a lot of background we can do gamma Ray spectroscopy.
Alex Gade: Now, at the microbiome cross section, so we can fish out very weak reaction channels and very weak.
Alex Gade: Partial cross sections from our PhDs, and this for this, you need to very good resolution of Christina or agatha and you need spec two graphs that select the.
Alex Gade: reaction channel for those pickup reactions at very high velocities or 60 me deeper nuclear energy they're completely momentum mismatch and they absolutely favor high orbital angular momentum.
Alex Gade: For the neutron proton to be put in, and they have to copper, to the highest moment total momentum in a scratch cascade.
Alex Gade: And so we stumbled upon this new excited state well above to MTV above the proton separation, energy and I think we could argue.
Alex Gade: Hopefully convincingly that this must be the six plus state, and we have specified the configuration that the State actually has.
Alex Gade: And so I seem to be good in time past few minutes over the next few minutes i'll show you the last example.
Alex Gade: which deals with the collective degree of freedom and it doesn't use Christina but it uses the Caesar array that I.
Alex Gade: Briefly, show to you and, again, thanks to all of my collaborators and, in particular.
Alex Gade: things to the graduate student Brendan longfellow who did all of this work, and he has done a lot more work also on the evening so far so top So if you need somebody to speak at your seminar series.
Alex Gade: This Brendan is now a postdoc at Lawrence livermore national lab and he can tell you all about suffice.
Alex Gade: So why we were interested in so for 43 this one has a rather illustrious history, which started with very beautiful and pioneering experiments at gunny the first.
Alex Gade: Evidence for ship coexistence in this nucleus came from time of flight mass measurements done by by wolfie and her and fed um and then few years later.
Alex Gade: moments were measured off and the shed coexistence was established by finding low lying isometric stayed close to the ground state and then.
Alex Gade: moments were measured of the ground state, and this isometric state and these indicate that those two States have different shapes so, and this has been linked to breakdown of the N equal to 28 Shell closer.
Alex Gade: prompted by work in SOFA 44 that even even a ball solid for 43.
Alex Gade: You talk about with you know made some very nice predictions about the nature of the ice of male not just inside for 44 but also inside for 43 So what we wanted to do.
Alex Gade: Is we wanted to quantify the collectivity, not just on the ground state, but also on that isometric state that that and collaborators from many years ago.
Alex Gade: So how do you do this and we performed a cool um excitation experiment with a beam of SOFA 43 that contains about 20%.
Alex Gade: Of the I samia okay so may have wanted 50 nanoseconds and it's a seven half minus Iceland, I should say, you will see the levels came later on.
Alex Gade: So now, if we perform column excitation and we have 20% in the ISO maybe a good chance to see cool on excitation on top of the ground state into on top of the ISO MIA.
Alex Gade: So how can we say something is on top of the ice samia we actually have a cesium i'll die total score at the end of the essay Talat focal plane, and we do sort of recoil tagging on.
Alex Gade: The scattered site for 43 is implanted in a aluminum plate before the horoscope and then, if it's in the ISO may receive the peak here that's the 320 K V.
Alex Gade: gamma Ray transition from the I samia, then we can request a coincidence, and say so, who came in coincidence, with this is oh man Ingrid Tina and we see a 1500 32 K be gamma Ray.
Alex Gade: This coincidence, or the statistics is a bit low, but we were fortunate enough that coupling boomers graduate student.
Alex Gade: did not knock out experiment, to the same nucleus and confirm that this transition is living on top of the ice, so this is whole season sees cool on excitation of.
Alex Gade: Soil for 43 and you'll see here some five some for transitions that can be seen, we performed your own simulations to decompose the spectrum and.
Alex Gade: If we don't.
Alex Gade: doppler reconstruct what we see is actually the isometric it's so short lived in the case in flight and it comes barreling down the beam pipe and decays and Caesar is it from the side or from the front face with this is oh man, this leads to this, we have background here.
Alex Gade: So what we always do is we measure angle integrated, cross sections for the excitation so that means we use the counts the gamma Ray counts over the number of particles and have been particles and target nuclei and we determine.
Alex Gade: The the chrome excitation cross section for all the different transitions we see, and then we use I didn't put the reference the.
Alex Gade: Winter older model of relativistic economic citation to translate those angle integrated, cross sections to be only two values.
Alex Gade: Our trick to keep the reaction at safe distances were only electromagnetic interaction dominates is we restrict the scattering angle, so that the impact parameter is.
Alex Gade: The sum of the two radio, plus a separate for, so this is what we measured in the experiment shown here the line sickness and the numbers are the Bo P two values and three transitions lip of the ground state.
Alex Gade: And one transition lifts on the isometric state as indicated here, and this is a shared model is stp of em you share model, and this was modified a little bit because the ISO me originally was at the wrong energy.
Alex Gade: And you see the picture is sort of right and within our larger uncertainties, admittedly, and we do agree, for the collectivity of the I samia, however.
Alex Gade: It seems to be that what we measure in the experiment is about factor of to a lower than what theory predicts, and this is very likely related to effective charges, and you can you can.
Alex Gade: Ask Brendan longfellow to tell you about that he's also working on a long paper about this topic for even even SCI fi isotopes.
Alex Gade: So over all of this picture of this shape coexistence is nicely reproduced, and this is my last.
Alex Gade: slide and it's extremely complicated, so let me walk you through this those are.
Alex Gade: view of E two or E two maps that Alex brown came up with, and what you see, is for each spin value one have three have so on, you see i'm excited states.
Alex Gade: As function of the energy and the dots indicate the magnitude and the sign of the quarter for moment blue means negative spectroscopic quadruple moment.
Alex Gade: Red means positive spectroscopic quarter point moment and the connections in between here are the VOC to transitions and the width scales, with a.
Alex Gade: Beautiful to strength, so you can see, there are some negative spectroscopic quad employment moment I saw merrick state and you see this collective structure built on top of it.
Alex Gade: And then you see other structures here that are clearly collective because they have white on connection and they all have like.
Alex Gade: Have the same quarter appointment.
Alex Gade: So now those those figures can be a bit overwhelming, but with one glance you can immediately say where are the collective structures in this nucleus and what's been values are involved in this quarter for call activity.
Alex Gade: And then I have color coded here some of those lines in blue and an orange, and the reason is that, in this theory paper, I pointed out to you before i'm the collective structures on the ground state and.
Alex Gade: First excited state ain't on the ISO males they are predicted to be very nice collective model.
Alex Gade: Structures built on a key one half and on the key seven half bantered and.
Alex Gade: If one takes the textbook calculation of K one K equals one half and key with seven half this is how it would look like.
Alex Gade: And now you compare the messy show model to boy models and textbook and you see this beautiful structure of.
Alex Gade: rotational model based on key with one half and seven half is reflected in this messy complex sharing model okay.
Alex Gade: So we were very excited about this and that actually inside for 43 with all of it states and all of its pov two values this beautiful textbook structure which is so shown here emerges.
Alex Gade: Out of the calculations, if one looks at those complicated in two maps.
Alex Gade: So inside here, we took a so so for 43 years 27 neutrons are 145 is 27 neutrons and we wanted to see all those beautiful structure surviving.
Alex Gade: And we just draw the same plot, and you see it's totally different okay there's no similarity between those two ISO tunes and the call.
Alex Gade: To collectivity is totally different and where those plots might be overwhelming I started to really, really like them, because they immediately tell you.
Alex Gade: about structural differences between different nuclear.
Alex Gade: So the onset of this nice rotational or collective structure is very sudden and it's absent in our 145 and with this i'm essentially.
Alex Gade: At the at the end, let me summarize the SOFA 43 for you, for the first time, be quantified the call activity on top of the second half minus islamiyah that was found 20 years ago now.
Alex Gade: And we found this to be brought in agreement with this show model calculations, and I should say I only showed SDP of em you share model calculations, this is the.
Alex Gade: interaction for this mass region from the Tokyo group but and fedex stp of em you performs equally well and there's no no difference really in those predictions.
Alex Gade: So then sort of prompted by you talk about with you knows predictions that those that there should be very simple structures inside for 43 we went and we use those two maps to map all these collective structures, and indeed we found.
Alex Gade: K equals one half and seven half structures that look, just like four modules and textbook description.
Alex Gade: Of of such collectivity and then we got curious and we're thinking does this survive neighboring systems and the answer is no, are going 45 just to protons above does not have any of these very simple structures.
Alex Gade: So with this i'm not summarizing all of the different science cases I presented to you I just hope I convinced you in this 45.
Alex Gade: Minutes that Indian gamma Ray spectroscopy was fast beams is really a nice approach to to address a broad spectrum of nuclear structure physics, as mentioned before, if you want to learn about.
Alex Gade: This kind of fast being in being spectroscopy for astrophysics you and you should attend Kevin lattes talk on Friday hosted by by gina.
Alex Gade: And i'm there is room for modest resolution high efficiency simulator arrays, for example in column excitation were not much level density is expected and you don't need.
Alex Gade: A high project high rates to perform those column excitation experiments and so those models revolutionaries they can complement a very powerful germanium tracking erase that we are using all over the world.
Alex Gade: And for me, the future is bright with this kind of approach and gamma Ray spectroscopy and, for me, in particular because soon effort is starting.
Alex Gade: And there will be a very exciting gamma Ray spectroscopy program possible in business, I thank you again for for giving me the opportunity to to be in England for like for one hour or so and not sit in the Michigan snow Thank you.
James Smallcombe: Thank you very much Alex.
James Smallcombe: So, yes.
James Smallcombe: Great talk lots of topics covered so i'm sure we have lots of questions, so please, if you have a question as said of the staff head down into the.
James Smallcombe: Participants menu in the I think I was told us in the reactions menu now use that raise hand button, or if you don't have a microphone put your questions in the chat I see digital clapping also people enjoying the talk.
James Smallcombe: i'm gonna get the ball rolling, and for the 62 chromium.
James Smallcombe: Yes, you seem you see quite strong population of the second zero Plus state so that would indicate as being popular strongly in the reaction mechanism does that.
James Smallcombe: Give it into the configuration which agrees with the Shell model calculation.
Alex Gade: yeah so that's a very good question, and let me see if I can get there quickly, so the.
Alex Gade: Yes, so 62 yeah so um the way the experiment was designed, it was designed as a pure gamma Ray spectroscopy experiment and we had issues disentangling which or how the chromium isotopes we are populated, so I have to go to this one, no.
Alex Gade: No, this one so chromium 62 as you see, in the upper spectrum was populated either by around 66 or by cobalt 68, so we cannot say how exactly it came about because those two guys we couldn't ID in the incoming beam.
Alex Gade: And so that also will fragmentation reactions, we remove too many nuclear arms to make physics statements.
Alex Gade: And to also be removed, what is it three nope leon's from manganese 65 so it's hard to uh because those reactions, they are not direct they can be.
Alex Gade: knockout reactions and then neutron evaporation and so on, but we actually do have plans to use the direct reaction and do exactly what you're asking about.
Alex Gade: And study those configurations using a direct reaction here um you know the experiment wasn't designed to really use the reactions for.
Alex Gade: Direct character and those are really fragmentation reactions, unfortunately, but yeah we have plans to use the direct reaction and then go exactly for the configuration of this gallery off of the state that the gamma rays coming from because.
Alex Gade: You think about shape coexistence and this region, this is really interesting.
James Smallcombe: Right okay look forward to that.
James Smallcombe: Okay, do we have any other questions.
James Smallcombe: don't see me raise hands right now in the chat window.
James Smallcombe: Okay, I will say this point, then, if i'm if you are struggling to find that raise hand button because they've updated zoom and hidden it.
James Smallcombe: Please go ahead and unmute yourself.
James Smallcombe: and ask away.
James Smallcombe: Okay, well, it seems we have a very satisfied audience.
Alex Gade: So I either put everybody to sleep, or it was unfortunately clear yeah.
James Smallcombe: i'm gonna assume it was the clarity.
Alex Gade: I will, I will go with that, yes, okay.
James Smallcombe: Well, well then, thank you, thank you again Alex for giving a fantastic token and taking time today to speak with us.
Alex Gade: It was it was great fun.
James Smallcombe: And and Thank you everyone for coming and enjoying the top and paying attention and.
James Smallcombe: I will, of course, as always, invite you back next week same time 3pm GMT on Monday, the 15th when we have a talk from Daniel Cox of Lund university will be talking about nuclear spectroscopy of super heavy nuclear accidents, the same time.
James Smallcombe: 3pm GMT next Monday, and I suppose I will be graduating on it also, we were told there's a nice top being run by gina on Friday with getting low so enjoy that if you're interested okay so have a good week and bye for now.
Alex Gade: bye bye thanks again.