 Hey, hello everybody. Thank you very much, Veronica and Anuak for organizing all this and for inviting me to give this presentation. And well, I, as Anuak said, I will be talking about chemical sensitivity in the X-ray for an infotainment aspect. Actually, there's an acronym one could use people. I'm not sure if this is established in the community yet. So maybe this one will stick. Okay, so this is what you see here. The beginning of the French Alps. This is where I work. I've been working for the past 15 years. And so this is I, here's, so this is a kind of a tutorial talk that I'm giving here. So the acknowledgments and principles should stretch throughout my entire scientific career because I learned so much from the colleagues and people I've been working with. So, so I ask you to carefully read and acknowledge the names that I put on the slides because many of the names there are colleagues of mine that I had a better working with. So this is part of the acknowledgments, the citations and names I put on the slides. I think also my supervisors and that goes a little bit to my scientific, yeah, my scientific biography. So I did my PhD with Van Zontag in photoelectron spectroscopy on free metal atoms at Hamburg University and then I moved to a group of Steve Kramer at the University of California at Davis. And they are working with Uwe Bergman, who was at the time a postdoc and scientist with Steve Kramer. And this is where we did the photo and infotain out spectroscopy, mainly in coordination chemistry and biopetalysis. And then I did a postdoc with Franke Roth at Utrecht University before then I joined the ISREF and at the ISREF we are developing instrumentation and applications for photo in for an out spectroscopy. And there I worked with many people and I'm grateful for everybody. Actually, I worked with the ISREF and currently the members in the group are Blanca and Sarah. They are like a human operation manager and nearly and it's a postdoc and Marius is a scientist working on theoretical. Well, and of course I think to show you now. Some books I looked what what the two days ago Jens prepared I think he proposed at least one of the books that I showed here as well. And that's for everyone. There's another book by Grant Hunker introduction to experimental fine structure, which is very good for a very good introduction for an experimentalist and you can check those web pages. And there's the international expert absorption society. This is actually also even sorry you should go to access.org and have a look there. And there are books. If you're interested. Well, this is recorded so you can go back. So there's the book actually from the 89 already by my son. This shows a lot of photo in photo out non-vision spectra and explain the theory behind this picture very nice in this review by myself and over and I think next week there's a talk by Sreena Sreena as well. So she has very nice many review papers on on photo in what an aspect. So this is also an extreme mission value support extreme mission. And I will just briefly address experiment because I think it's nice to do those who have not heard about this to at least know what can be done using this technique. So the father of this technique is Winfried Schülke and he wrote a book in 2007 Electron Dynamics by Inelastic X-ray scavenger. And then there's a review paper by Jean Pascal Reif and Arie Schuchler. It is also a very nice, very nice review and accessible in the experiment as well. In the talks I saw Jens advertised this as well by organized by Jerry Seidler in Washington State in Seattle. This X-ray absorption journal, journal club and there are many videos and also introducing various techniques. Okay, so let's go to the beginning. So I talked about X-ray emission or X-ray fluorescence spectroscopy, which is actually the first technique if you compare X-ray absorption emission spectroscopy. Emission was the technique that was used first and in order actually to establish the periodic table. It was an anniversary last year for the periodic table and there's Henry Mosley who realized that the X-ray emission lines are the energies of the fluorescence lines. They depend on the atomic charge. And that was important because at the time chemists maybe try to figure out how the periodic table is organized by looking at the atomic mass. It was possible and easy to do, but this was not leading to the final conclusion and the final periodic table that we have now. So the technique was required that is sensitive to the atomic charge. And X-ray alpha lines, capital lines, fluorescence lines, X-ray emission lines, they are sensitive. The energies, this is shown here, so the energy relates of course to the wavelength and depends on the atomic charge. So that was very important. So X-ray fluorescence has been around for a long time. And it's actually now a little bit rediscovered at the various in the labs and the significant variation sources because of improved instrumentation. So what can we do with X-ray spectroscopy? And I show here the theoretical absorption edges and theoretical fluorescence lines and experimental data. This just comes from tables. And of course it's element specific. That's very important if you ever write a proposal for an X-ray spectroscopy beam line, you should say that you wanted to spectroscopy because you need an element specific probe of the same. And not only absorption lines are, they have absorption edges that depend on the atomic number, but also then the emission lines that are sensitive. And of course you do this because you would like to obtain information about the sample, so about the electronic structure and the atomic arrangements locally around an absorber atom. And this is the information you can look for and you can extract from the X-ray spectrum. But it's very important that you can do this on samples without long range. So if you do the fraction experiment, you need some kind of long range order. And this is not required in spectroscopy. That's an important point. So if you have samples, for example, environmental sciences, you just want to put a piece of soil and see what the chemical state of whatever is inside this soil is. You don't need the long range order. You can any amorphous or polycrystalline sample. And if you do hard X-ray spectroscopy, but also in the soft X-ray range. The peak is bulk sensitive, especially in the hard X-ray range, bulk sensitive. And since the penetration is rather penetration depth is rather large for the X-rays and presence coming out. And you can do the X-ray experiments. You can put your sample inside a cell with a window in front in order to keep a certain gas environment around the sample, heat the sample. So this can all be done. You can do high pressure experiments in the end of the cells because of the high penetration of the X-rays. Justification why you would like to do X-ray spectroscopy. Okay. And what can I learn from X-ray spectroscopy? Here I group this into if you do low energy resolution spectroscopy. So this is for those who know this, if you have a mainly detector or anything that's sitting next to your sample, you have an energy resolution delta E of roughly 250 electron volts, which is two orders of magnitude larger than the coho lifetime. Here, if you do this kind of spectroscopy, so where the instrumental energy broadening is much larger than the coho lifetime broadening, then you can do an elemental analysis. Okay, that's an old technique here, everybody, but we would like to learn more. So we need high energy resolution spectroscopy where the instrumental broadening is on the order of the coho lifetime broadening or even much more in the melee electron range. Yeah, and this is shown here. So then if you have this better resolution using crystal analyzers, for example at the beam line, you resolve the fine structure of in this case the iron alpha line. And in this case, there are two different spin states of the iron sample and you see there's a chemical sensitivity. The high spin system here in the dashed line has a different shape broader a alpha line and the low spin system. Yeah, so if you do it with high resolution suddenly you see the chemical dependence in the X-ray vision line. So what can you do, you can see the local atomic configuration with this technique. You learn about the electronic structure, band structure for example oxidation spin states can characterize the chemical bond, you can identify your local coordination, the ligands inter atomic distance and if possible. And you can learn about magnetic properties right there techniques. In particular, a magnetic circular dichroism x-ray magnetic circular dichroism that tells you what magnetic properties and of your samples. So this is also possible. And if you do time resolved, I think what Jens showed two days ago time resolved and you learn about genetics, for example, if you have very good resolution, for example, in elastic x-ray scattering you can also learn about vibrational properties, molecules, for example. And so this is just a selection of what you can learn. And before I move on, I just would like to advertise a program here. So if you're interested in initial spectroscopy, you can use a code here that was written by, so user interface here is written by Marius Litigan at the USRF and that is based on a code written by Scott, who's a university of Heideberg, he wrote a code that's called 20 and that allows you to calculate an inner shell spectra within the Ligand field magnet approach. And it's a very nice code, it's written in Python, so it's an open source, everybody can contribute and see what happens there and there are many different techniques now included in this code. There are many different symmetries around your absorber atom and the various effects that you include in order to model the chemical bond, mixing of orbitals and the Ligand field. And it runs on all major operating systems. So if you're interested just go to the black page. This is pretty educational, by the way, if you want to learn about the Ligand field magnet, the effect of magnet spitting spitting, if you're familiar with ten hours of data diagrams, things like this, you can all model this using this code. So it starts to clarify some expressions or, I don't know, yeah, terms that we use, what is the soft X-ray range, you can say roughly below X-ray energies below 1000 electrons, and if you have energies higher than that you can call them hard X-rays. You can see this plot on the left, the attenuation length in many oxides and you see it's a well below one micron in the soft X-ray range. And then if you go in the hard X-ray range it goes to 10s, around 10 microns. And here on the right you see the transmission through air, that's the dotted line there, so through air, one centimeter of air doesn't believe that much of soft X-rays through, but in the hard X-ray range I can leave my sample in gas and pipe. And the energy range between 1000 and 5000 electron volts has recently been named the 10-day X-ray range, which was it also, scientists have a heart. And this is, yeah, I think it's generally accepted that you, in X-rays, it's worth, yeah, it makes sense, because in terms of instrumentation and absorption, actually it's a special energy range that has, for example, the K-H issues of salt, chlorine and phosphoryl and polylenzol, X-ray spectroscopy, and why it can show you something about the chemistry in your sample. For example, if you want to identify whether chromium is carcinogenic or not, and it is carcinogenic, if it's the oxidation state of chromium is 6, it's a hexavalent, and then it's carcinogenic, and you would like to avoid this. In 1985, there was still a lot of chromium 6 produced in the world, but now, at least in the European Union, it's been prohibited. It was the topic, some of you have seen this movie there with Julia Roberts fighting against a mean company who dumped a lot of chromium 6 into the environment. And you wonder how can I find out whether a piece of soil has chromium 6 or chromium 3, and the answer is you measure the absorption spectrum. You see it clearly, so this is the K-H, K-absorption edge of chromium, and if you have chromium 6, you see this strong line here, this free peak coming up, if you have chromium 3, you don't see it. And why the spectrum is so different is because chromium 6 is 4-coordinated in a tetrahedral local environment, so there's a chromium here in the center and the vegans around. And if it's chromium 3, you have 6 vegans around in an octahedral geometry. Octahedral geometry is a higher geometry, has a higher symmetry than the tetrahedral symmetry, you have inversion symmetry. In this case, there's no inversion symmetry for a tetrahedral complex. And the inversion symmetry prohibits mixing of orbitals, in this case it prohibits mixing of P and D orbitals. In this case, mixing of P and D orbitals is allowed. The mixing of the P and D orbitals makes this free H peak here so strong. So in this case, the K-H pros the local geometry, and from the local geometry we can deduce whether it's chromium 6 or chromium 3. Yeah, so this is a nice example I actually stole from the web page of John Bada, it is Israel, but it's very nice example of how X-ray spectroscopy can be used in environmental sciences. Another example here, this is local, this is together with Alonso at the University here in Nobel, who is an expert on chemistry and mercury. And we measured the L3 edge, what that means 2P excitations in mercury and this is sort of high resolution zanes, as we explained later. And we looked at the mercury L edge, the mercury in human hair, and the mercury in the human hair ended up in the human hair either by eating too much fish, tuna, swordfish, whatever. Or by having your dental amalgam removed, then the dentist is not careful, the mercury in the amalgam goes into your body and ends up in your hair. And the question was, can I distinguish between the mercury coming from the dental amalgam or from the fish, and then you measure the absorption edge, and you see the spectra difference here. Below here you see actually measured at EOSF ID 21, and with the microscope, an X-ray microscope, if you scan along the hair in this direction, and suddenly you see the spike here, that means you can calculate that when the dentist removed the amalgam from your hair because then in the end, this is when you put the mercury in your body and then the hair grows and then at a certain point in your hair, you find it again. It is very low concentration, this is also in the parts per million, parts per million, in the low parts per million, in the PPM range to measure those data. And the point here is that the local coordination, so these are proposals how mercury is coordinated. If you, if it ends up in your hair after fish consumption and it ends up in your hair after having your dental amalgam, and you see that the coordination is different in the two cases, and this can be done by, so the assignment between the structure and the spectrum shape is in this case done by measuring many, many, many model compounds and calculations, theoretical calculations of the structure of the measurements and then the structure is inserted into a theoretical code. In this case, the FDMDS code by each of these, and this then leads to this assignment of the spectrum features to the two complexes here. Okay, so this was a good motivation and now I would like to explain to you some basics, it will get a little mathematical, I hope it's not too heavy, but I think it's useful in order to understand the background of basics of X-ray spectroscopy. So first an overview of the different things that people like to measure in X-ray spectroscopy. So I show here one electron diagram of various transitions in a 3D transition metal. So this is the Fermi energy, so you have all those levels here populated and not populated. If you excite from a 1S or 2P shell, you can excite the electron either to the continuum, or you can excite into an unoccupied orbital just about the Fermi energy. So this would be a resonant excitation that would be a non-resonant excitation. So what you can do now if you, you can measure for the kinetic energy, of course, of your photoelectron and then photoelectron spectroscopy. This is particularly interesting if you go here to the right and photoexcite an electron from the occupied valence orbital and then measure the kinetic energy. Then you get the spectrum here, that could be photoelectron spectroscopy of your valence shell. You can do this also, of course, of any column. So that's photoelectron spectroscopy. But after following the creation of a cobalt they can see, so you create a 1S or 2P hole, and this hole is then filled either from the 3P shell or from the valence shell. Then you call it K alpha, K beta, or valence to core X-ray emission lines. In case, since the photoexcited electron is too high up there in its photoionized state, this would be called a non-resonant emission spectroscopy. If you do this following a resonant excitation, you would call this resonant emission spectroscopy. This is in principle resonant-inertic X-ray scattering. It's all the same thing theoretically as you can call it resonant X-C-S or resonant-inertic X-ray scattering. Of course, they are shown already here as well, and I hope you will know this, and this can be called the resonant valence to core. Okay, if you do this in the hard X-ray range, the X-ray absorption spectrum, if you excite from the 1S electron, would be the blue line here in main denies, and the valence to core, this line here would be the green line here. So this is just to explain to you, to show to you, so this provokes the unoccupied orbitals in this provokes, and occupy them all. The final thing here, gross photomission, I'm not explaining now, you can look at that. Okay, this is the, yeah, also I would like to, another point that is important to me in order to better understand the things that I'm showing now. On the following slides. So I showed you now the transitions here in the so-called, I call this one electron diagram, right? We showed the energy of the Fermi level here, and we excite the 1S electron into the continuum. So I showed the levels of the orbitals, the energy levels and the qualitative scheme of the orbitals here, Fermi energy and anode. Okay, we discussed this before. And I can show exactly the same thing in the so-called many body diagram that observes the energy conservation, neglecting the energy of the photon, but the energy of the, of all electrons in the system. So that means that the non-resonant excitation here, I show like this, the ground state is described by all electrons in my system, so it's not a single shell, it's the energy of all electrons and photons and everything included in my system. Yeah. And I go from this into this state and I have a photo electron excited here. That would be the resonant excitation where excited 1S electron into the 3D auto and I reach a configuration 1S1, 3D and plus 1. Yeah, so again, this is a multi-electron description of this excited state that I reach after this resonant excitation. And if I now want to describe my k-beta lines, I reach, in this case, this is the non-resonant k-beta line, I will place 1S hole, 3P hole, and this electron just stays up there. So this, this is this electron there, it just stays in its H1P state. And then the resonant, the resonant emission, so this is the k-beta section here with the excited electron staying in the resonant shell, and this goes down to this state there. And so this is then the one, many electron, many body description of the same process. This has many advantages because as I said, it observes energy conservation. It's the more useful way of describing your transitions, and it's easier to show the two-step processing. Okay, so how do we, how do we calculate this? So again, this is the total energy diagram, I go from the ground state and the excited state. The energies of those states are calculated using the Schrodinger equation shown here, and which is then put into some codes, can be a DFT code or any code that gives you then the energy of those states. And if I now want to calculate the spectral intensities, I have to calculate the so-called transition matrix element. So I have the wave function with all electrons included in the ground state. I have an operator here that represents the interaction of my x-rays with the electrons in the sample, and this is the excited state. This is the transition matrix element, I take the square in order to get the intensity. And then I do an approximation. So I want to get rid of all electrons that do not take part in the transition. It will still somehow affect the spectral intensity because they will rearrange as a response to the photo excitation. So I have one electron orbitals here, so this could be 1s, and this could be 2p, 3d, depending on what element you look at, and I simplify the photon operator to the so-called dipole operator. And the effect of all other electrons that rearrange is just long together in the spectrum. Okay, and this is the same thing written, so this is just the short form, the rack notation, and this is then you just, what you have to do is solve an interval with the dipole. So here, just for your reference, I show how the excitation operator here or the operator that represents the photon can be rewritten or approximated into the dipole term and the particle term. Okay, so this is what is calculated in order to calculate the spectral intensities. In those cases, so it's a dipole transition between one orbital, for example, 2p into a 3d orbital for the energy of a 3d transition. Okay. And let's go to take a step back and go back in history. So how was observed and described in 1792. There are no, which is kind of an empirical law that shows that the intensity after a sample is reduced compared to the intensity before the sample by this exponential factor. And the tau here I can then describe in more detail by the, what I put everything there, by the particle density and here this is then the atomic cross section of the homogeneous sample of the atoms in the sample. And I think it's a little bit more complicated if you have a heterogeneous sample, several elements, and in the sample, it's just the sum over the cross sections of the different elements in the sample. And, and this considers in homogeneity of the travel direction. Yeah, so what the point is here so the, so this is kind of the empirical observation, and you relate this empirical observation to an across section. And the atomic cross section of the element in question. Okay, and this is actually the thing that contains the function of energy, and this contains, ultimately the chemical information that we're looking right so we want to describe this or measure this in our experiment. And so this was now what the status of, let's say 1792. If you can now go to modern quantum mechanics quantum mechanical description of the process we can, it looks like this so you describe your incoming photon, the, with its energy, the wave vector, and the polarization, the same the outcome in photon energy wave vector and polarization. And then you have the incoming and outcome shown here and then you have an angle between the incoming and outgoing photon which is the scattering angle, and between the two photons incoming auto photons you can define a momentum transfer you. Okay. So that's the result of quantum mechanics done, obviously I don't want to go into details there just say that the photon here is described by a vector field. This is the plane wave just traveling in this direction. And this is the. Yeah, so this is the vector field a that describes the photo. See then in the next slide that I can distinguish the spectroscopies that I do. I can distinguish what how a is treated in the perturbation theory so this vector field perterbs the electrons in the in the sample. And this is quantum mechanically treated using perturbation theory and then they have several orders of perturbation theory there's a first order and the second. I have an order I have an a square term and the second order I have an A dot. Yeah, so what is important here just I have the first order term and the second order term where this a appears different. A little side remark that if you want to relate the cross section that I mentioned before for the total absorption. There's a so called optical theory that relates the absorption cross section to the elastic forward scattering in the sample so forward scattering is zero. Okay. Yeah, so the principle in this. And I have actually the next question. Yeah, questions. Okay, yes, there might be some connection issues today. But if anyone in the audience has a question. This is the time for questions seems so usually the way to the end according to our experience. Okay, so I, so what I go back to the. Yeah, so that is important now you have the you you you describe the interactions of your x-rays with the sample into in using the quantum mechanical perturbation theory, then you have a cross order time in the second quarter. And by months you obviously don't have to understand the details, but I just want to show you that the so called first order terms and this is your sample and this is your photo coming here they interact in this case the photo comes out and your sample goes in a different state. In this case this is the so called a square term. And if you go in a in the so called second order term people p.a. This is your sample and this is your photon and here the photon is absorbed, there's kind of a photon less intermediate state, and then the photon goes out, and the sample continues. Okay, this a square term, just to make the link this a square term, the formula here is, is not so just for your information. So what is important here is that there's a stock product between your incoming and outgoing and outgoing light. This product gives an angle of dependence to the, to the intensity here. And there's elastic scattering, Compton or Bragg scattering is elastic, Rama scattering, Compton scattering are so called inelastic. Okay. And here this is the, what I explained before so this is the wave momentum transfer, which is the difference between the incoming and outgoing and wave factor. Okay, and the operator here so this is again the ground state in the final state and what is connect what connects the two ground and final states it's a transition operator, and the transition operator contains this momentum transfer you. It's very interesting because that, if you think of selection rules that determine this transition here, the momentum transfer Q influences the selection rules for your transitions. And using this, you can do spectroscopy as you can do spectroscopy and it's very interesting it's called x-ray Raman spectroscopy and so again here the matrix element that they have to calculate and this is the study by Asimov Wotary and Etel Sinki, who has very nice papers there that explain this Raman scattering. So what you see here, this is the Compton peak, the broad line here. So this is measured I think at roughly 10,000, 10,000 electron volts incoming energy. And if you change your momentum transfer, and you see how the Compton peak changes, this is, this is what I know, and what is nice that you see here something like an absorption edge. So in this case Seymour scattered 10 KB photons from a diamond sample and change then it could be changed the scattering angle, and that changes the Q, the Compton peak moves around but this line here does not change. It stays at a fixed energy transfer. So it's an energy that is transferred from the 10,000 electron volts incoming beam. It transfers roughly 300 electron volts to the sample. And at this 300 electron volts I see an absorption edge. I see the carbon K edge that I usually can only observe using soft x-rays. So I could do absorption spectroscopy at the carbon K edge directly at 300 electron volts. But using this X-ray Raman scattering technique, I can observe the carbon K edge by going into with 10,000 electron volts and look at an energy transfer so I look at outgoing x-rays with 9,700. This is called X-ray Raman spectroscopy so it allows to study loads and elements using hard x-rays. And this is interesting if you wanted to research in batteries for example, where in this case, you look again, you look at the carbon in this battery. So this is an in-situ experiment. So you see there are several windows, the graphite electrodes, separators, and the lithium compound electrode. And different voltages are applied and the carbon in the sample changes depending on the voltage. And I can slightly measure in-situ the changes of the carbon chemical environment using these X-ray Raman spectroscopy. Again, so this is here the energy loss. So this experiment I don't know exactly details, publication references here. The experiment was done at again roughly 10,000 electron volts or several KED. Yeah, so this is a very interesting technique. This is the X-ray Raman technique. Are there any questions? We have questions actually. As I said, they come later. So one question is, which X-ray spectroscopy is more suitable in case if we have barium and cobalt together in our sample, having nearly same binding energy? Yeah, but barium and cobalt. Yes. Yeah, they can easily distinguish them. The absorption edges, I think you should be able to distinguish them. If you have problems with it, that's a long question. If you have problems with X-ray ranges, then I don't know exactly what the copper is like and something. Barium, if you have problems with X-ray spectroscopy and edges coming up, that's a different topic. Okay. Yeah, there are others. So maybe we take another one and then you can continue. Okay. Good. So what should be the minimum sample volume for those techniques? The sample volume is, depends. In business, the beams are very small. You have microns or even nano beams, right? That would be your sample volume. The problem is that you probably fry your sample with small beams. If your sample, yeah, the volume that you need to respect is very small. I think it can be in the micron range. But if you fry, if you burn, if you damage your sample with the X-rays, you need a lot of sample because then in order to get your spectrum out, you have to change your sample many times. So you have to move your beam on the sample. But the beams can be much smaller than neutrons. Neutrons need larger samples. X-rays can work with very small beams. Okay. Then I think you can continue because the time is running out, so it's 240. So let's go now to the, to the second part of this interaction. So this p.a. is what most of the spectroscopists are interested in. Again, so these are your, your scattering and defection experiments are this term there. Environment spectroscopy is a special case of an inelastic X-ray scattering experiment. And this is what most of us spectroscopists are interested in. And so what you do, if you do photon-in, photon-out spectroscopy, again in this total energy diagram that I explained before, you start with the ground state. You calculate, you have a certain probability to reach intermediate state, and you have a certain probability to reach the highest state. Okay. And this can be calculated with the Thomas Heisenberg equation here. I am not going into detail. But it's interesting, you can vary the, the so-called energy transfer, right? If you, if you have a high energy transfer, you have the cobalt in the final state as well. A shallower cobalt then in the, in the ground state. I'm sorry, in the intermediate state. And you can reduce the energy transfer, and then you see actually very small energy excitations, and then actually your X-ray spectroscopy states that are similar to your optical spectroscopy. So if you do, another electron 3D goes out, that would be a rather large energy transfer. And if you have a transition in the second step from the valence orbital down to the cobalt that you created before, the 2P cobalt, then you have a net excitation that looks like you excited an electron from the valence orbital to the unoccupied orbital there. And this looks like an excitation that you can observe in optical spectroscopy with the UVVIS spectrometer, for example, in your lab, or even a Raman spectrometer in your lab. Yeah, so you can have, using X-rays, you can reach an excitation that are usually only observable using optical means in the lab. If you do it resonantly, then you observe this excitation element selectively. Yeah, there's another way of showing this. So if I go with the X-rays in, the X-rays out, and I have an energy transfer, and this small energy transfer allows me to observe vibrations at the valence, for example, in my inelastic X-ray scattering experiment. Okay. Another way of showing this is just an overview so you can, you can, you can study using this inelastic X-ray scattering by reducing the energy transfer. You can see, you can see four phonons, you can see crystal field interactions, you can study your charge transfer excitations, and if you go higher energies, higher energy transfers, you see them, the core levels in your inelastic scattering process. Okay. Now I give you an example for, for serum dioxide to see how this works. This is P to 3D, to 5D in this case, so serum is a rare earth, but D levels are unoccupied. So if you measure an LH spectrum, we said 2P to 5D, and then you can observe a 3D electron going down to 2P. The second order process has to be described as Thomas Heisenberg equation that I showed you before. So I analyze the, not only the incoming energy, but also the scattered energy, the fluorescence energy, and I get two spectrum, this spectrum and this spectrum. I can combine the two spectrum, and I get the so-called ring strain, the energy of the incoming beam shown here or the energy of the outgoing X-rays shown here. I can move on the parameters and get a two-dimensional intensity distribution. What I can do now, I can take the diagonal cuts to my, to this two-dimensional energy distribution, and I get this red line here, which is called a high energy resolution fluorescence to take the X-ray absorption spectrum. And I can compare this to a conventional absorption spectrum. That I would measure, for example, a transmission moment or total fluorescence. And you see that this diagonal cut, so this kind of Riggs technique allows you to improve your spectral resolution enormously. Yeah, so I see I get a spectral broadening principle that's not limited anymore by the left and broadening of my interface. And this shows again, so you have a 2P hole in the, this is intermediate state, a 3D hole in the so-called final state. You see this in orbit splitting of 3D levels here. And again, you see this broadening in the actual before. It was done a long time ago, actually, by K. O. Hemmerlein already on this prosium in 1991. So I just explained to you here why, where this, where the broadening comes from. And the second broadening comes from your lifetime broadening of the intermediate state is stretches in this direction. I can go in the final state in this direction. And I can do a cut through this Riggs plate at 45 degrees relative to those broadening. And that gives me the spectral sharpening. This has been used another example here by an arm also I'll just show you what can be done there on mercury. The gray line here is the conventional spectrum that you measure in conventional absorption spectroscopy. And the blue lines here, they show you the high resolution data. Using crystal analyzer spectrometer in order to analyze high resolution, the fluorescence coming out. And you see the, how you, how you can nicely distinguish the high resolution data between different coordination. So if you have linear coordination, you get this strong HP. And if you have six coordination becomes weaker, and it becomes even weaker. Yeah, so it's similar to the chromium. The edge spectral shape highly resolved allows you to identify the local coordination of the mercury in the system. Another example here to do for you can also do this in the tender extra range. So this is uranium. This is the fore edge of uranium. If you measure it conventionally, you've got red lights here. If you measure high resolution, you see you can suddenly resolve all this time. These are the same samples, low resolution, high resolution. This really allows you to distinguish in mixed data compounds. So you have uranium, uranium four and uranium five you can distinguish between two in high resolution data. So this is a work by Christina and this is actually a topic these days so many people want to do images and actinides using this high resolution. So this is a really allows you to obtain much more chemical information about the same conventional job. Any questions? Yes, we have a question on how to see the changes in a molecule with the different ligands. And how do we know which one is causing those changes, which which ligand is causing those changes. I can show you a slide if you want to see how you can identify a ligand. Yes, it says how to see the changes in a molecule with the different ligands. How to change. So their ligand identifications don't pick topic of ligand identification. In principle, there's XS, there's a lot of literature and XS on the net. And if you have ligands with very different atomic numbers. For example, if you have a metal ion that is usually only oxygen ligands, and suddenly one or in the high coordination shell there is another metal ion. You should see this metal ion in the XS. XS has the limit. XS is not able to distinguish between ligands that are very similar in their atomic numbers. And if you want, I can show you quickly. Yeah, we need to just continue because I, I, I show you I show you I did that answers the question. So, in this valence, valence to core x-ray emission spectroscopy, you are, you, you see those transitions here. And their transitions they relate to the binding to the binding energy of the 2S electron on the ligand. And this valence to core emission spectroscopy allows you to identify the ligand of the ligand. And maybe Serena next week she will talk more about valence to core emission spectroscopy. So if the question is how can I identify ligands, you can use this valence to core x-ray emission spectroscopy. Thank you very much for your answer. We have 10 minutes left. So I asked, maybe I ask you to continue with your talk and then we leave the few, maybe a couple of questions for the end, right? Mm-hmm. Okay. Well, how, how, how much longer you want me to talk? Want me to talk? Just for me to know. I mean, if you're, if you're, if you're done, then we can continue with the questions. If you have a couple of slides to show us. Then I just, well, I'm sure this is the last thing that I showed, maybe then I expanded a little bit, a little bit better because I, yeah, so the, the, the valence to core emission lines, they come from, from, from mixed orbitals. So they're, they're orbitals, where they, this is the metal ion here in the, in the, in the center. And the, the, the orbitals, 3D orbitals, also key orbitals. On this metal ion, they're formed together with the ligand orbitals. So these are six ligands around and these are 2P orbitals on the ligand. They form molecular orbitals that are composed, like in a linear combination of atomic orbitals, they're composed of the metal orbitals and the ligand orbitals. Yeah. And this can happen for by mixing the 2P ligand to P orbitals, the metal orbitals or the ligand to S orbitals with the, the metal orbitals. So these valence to core emission lines, they arise from occupied orbitals that are mixed orbitals between the metal valence orbitals and the ligand orbitals. And that makes those valence to core emission lines sensitive to the ligand environment. Yeah. And that's why this, the line here comes with X. So this, these lines here, they are the rise for molecular orbitals that are mainly composed of the ligand to S orbitals. And that's why the energy of this line that I observe in my spectroscopy relates to the binding energy of the 2S electron. Yeah, so this allows me to identify the ligands. And it goes, you can compare this by the way, the valence to core extra emission lines, they reach formally the same electronic final states as valence by valence and UPS showed at the beginning. And so you can compare for chromium oxide. So this shape here, you would have to compare the chromium oxide here, which is the red line there, so only this line here. Yeah. So principle it probes the same part of your, of your electronic structure, different selection is different energy resolution so the spectra look different. This technique is element selective valence band UPS is up to you if it's not done, residency, not an element select. Yeah. So this is done under usually under ultra vacuum condition. This is done x-ray emission spectroscopy in any kind of environment if you want to use hard x-rays that are compatible with any kind of x-ray environment. Yeah. And we use this there and for example to identify in electroplated samples to what extent I have metallic chromium or chromium carbide. And it does take very nicely using the test code, for example, anybody familiar with the test code, you can calculate the spectra it comes out quite nicely and you see the difference between the chromium metallic chromium chromium carbide just open it up. to speak here in the x-ray emission data. Okay, so this is a very nice tool to identify your liquid environment. It goes further, you can even see this in model calculations done by Kligowitz-Wohlensepp, who's now at the PSI. If you have a hypothetical system of manganese in the center here and six water molecules around, you can see or you can detect in the spectra whether one of the six water molecules is missing one proton. So if I replace a water molecule with a hydroxide, then this shows up in the spectrum. Why? Because if I remove the proton, the binding energy of the 2S electron in this oxygen here will change. And I can then sign actually this molecular orbital that is mainly localized in this oxygen there has a different binding energy and then that's a different present energy than in the water molecule that is here on the other side. So on the other side, I still have water with two protons and the energy is different. Yeah, so the bottom line here is that this technique allows you to identify the degree of ligand protonation in your sample. Yeah, but the reasoning, the chemical sensitivity is always the same. Yeah, I look at the fluorescence line that is sensitive to the ligand environment. Yeah, that's sensitive and then to the binding energy of your ligand energies. And with this, I thank you for your attention. Thank you very much. We continue with some more questions before the end of this webinar. So one of them is how flexible is the technique instruments? Can I measure thermal excited reactions? Yeah, this is, this is, it's hard x-rays or even tender x-rays. You can easily build an in-situ cell. So you can heat up your cell up to easily up to 1000 degrees. For example, you can go even higher, people do experiments in extreme conditions, right, in order to simulate the conditions inside the earth or even on planets in the universe. So people with, you know, elaborate setups laser heating and you can go to very high temperatures and very high pressures. Yeah, so very, yeah, all kinds of samples or conditions for the sample are possible. Great. So we have the last question then because time is running out. So at the start you said about, you said something about sample damage. So how to address the sample damage? Yeah, that is a long topic and a very important topic. You only have two minutes. Because, yeah, so damage, every sample you put in the beam you should check for damage. Yeah, if it damages under the beam, you have to think of a new experimental protocol, you have to change, you have to move the beam over your sample or change the sample many times. To do, you should calculate, somehow estimate how much, how many photons can I get out of my sample before it's completely damaged. And then you can calculate whether the experiment is possible or not. It may be, if your sample damages under the beam, you need a lot of sample. If the amount of sample that you have available is limited, your experiment may not be feasible. It's as simple as that. You can try to cool down your sample, you can put your sample into vacuum, there's certain mitigation methods. You can try this and you need almost even around the world, they all experience and they try all of this, and sometimes even cooling down your sample.