Interview: Hans-Peter Steinrück
2017 AVS Medard W. Welch Award Recipient
Interviewed by Richard Brundle, November 2017
BRUNDLE: Okay. So my name is Dick Brundle, and I’m representing the History Committee of the AVS in our Oral History Project. Today I am here to interview this year’s Medard Welch Award winner, and that person is Hans-Peter Steinrück. I’d ask him now to introduce himself. Just say hello.
STEINRUCK: Hello. I’m Hans-Peter.
BRUNDLE: Yeah. I think we can distinguish the two voices okay. [Laughs] So I’m going to start off by reading the citation for the award. “For his pioneering studies on the properties and reactivity of the surfaces of ionic liquids employing the methods of surface science,” which is actually only a small part of your scientific background, and I guess the most recent. So congratulations on the award. I want to ask you about where you were born, where your parents came from, their background, and a little bit about your early history because that doesn't appear in any description here about your science. Then we’ll take it on through there up to the present time.
STEINRUCK: So yeah. I’m Austrian, and I was born in Salzburg, the city of Mozart, in 1959. I grew up in the mountains south of Salzburg in a small village called Radstadt.
BRUNDLE: You know, this is amazing because every person I’ve interviewed this time, and mostly in interviews, comes from small villages somehow. They start off there. That’s happened every time!
STEINRUCK: It’s funny, yeah. So it’s a small city, an old city since the 1200s, something with 3,000 people. Yeah, maybe this is interesting. In the city, there was the judge and there was a guy taking care of the forest, which was my father, and then there were three doctors, but no high school. So at one point my father and the judge, I guess over a glass of wine, decided to found a high school so that their kids would not have to travel one and a half hours one way to go to high school. At the end, the judge and my father founded the school, a “gymnasium”, 50 years ago.
BRUNDLE: And you were the first pupil there?
STEINRUCK: No, I wasn’t the first. The school started in 1967 and I got my high school degree 10 years later; so the founders were sort of planning in advance for their kids. We will have the 50th anniversary celebration at the end of the month and I will go there.
BRUNDLE: For the anniversary.
STEINRUCK: Yes, for the anniversary of the school.
BRUNDLE: But you said your father was in charge of forestry.
STEINRUCK: Yeah.
BRUNDLE: So his background was…
STEINRUCK: A forest engineer. He originated from Vienna, and my mom comes from the area. They met and then he found the position in Radstadt and then I grew up there.
BRUNDLE: Any brothers and sisters?
STEINRUCK: I have a younger brother who studied law and music, so nowadays he’s a professional musician. He didn't know what to do, so he first studied law, because the best friend of my father was the judge. After he finished his PhD, on the day he got the certificate, he told my parents, “I’m going to study contrabass now,” and ever since then he’s a musician and lives of it. Might be interesting for you, because you are organizing bands, I’ve heard?
BRUNDLE: I don't play in bands…
STEINRUCK: But you organize.
BRUNDLE: …but I organize music—promote it, I suppose. I know a lot of musicians, and actually I do know two or three who were trained as lawyers and never practiced…
STEINRUCK: … indeed, he never practiced.
BRUNDLE: …or just very briefly and have made their careers full-time as musicians.
STEINRUCK: He’s a doctor in law and he said, “You know, the real funny thing is - anytime there’s a contract and I have to put down my name with the doctor in law title (this common in Austria), everybody’s starts to be extremely respectful”, even though I do not have any clue anymore [Laughter] It’s funny. So yeah, I grew up in this village, went to elementary school and then to high school there, and then I did my service in the army in Salzburg.
BRUNDLE: What age is that?
STEINRUCK: That was 18, so directly after highschool.
BRUNDLE: And it’s compulsory.
STEINRUCK: It’s compulsory.
BRUNDLE: Still?
STEINRUCK: It’s still compulsory—different to Germany. There was a vote like three years ago in Austria on whether it should be compulsory or not, and now it’s still compulsory. But you also can do civil service as an alternative. Then, after my army service, I decided that I wanted to study physics. Already when I was 14 or 15, I found it very interesting and that interest continued.
BRUNDLE: Is that an influence from somebody at the high school? Did you have a good teacher?
STEINRUCK: Yes, indeed. In the eighth grade and then in the later grades, I had very good teachers, very motivated teachers. They realized that I was sort of gifted in that direction, and they supported me. However, my father wanted me to study electrical engineering because that seemed to be a job that pays. People in the countryside don't know what a physicist does.
BRUNDLE: Probably doesn't pay as much as a lawyer, but it pays, yes. [Laughing]
STEINRUCK: That’s true. The other thing is there is no physical industry. There’s a chemical industry like Bayer or BASF, but what is a physical industry? There is Siemens, maybe, or Infineon and General Electrics, but that’s not so familiar with people. My father wanted me to study electrical engineering, but he was very wise in the sense that he went with me to Graz, which was the next big university where you could study a technical subject. A son of his friend was—how would you call it?—sort of a senior scientist in electrical engineering and he got me in contact with this person, hoping that he would convince me to study electrical engineering. But this guy was really nice and said, “What do you want?” I said, “Study physics,” and then he said, “You’ll study physics.” [Laughing] “That’s the only meaningful thing to do!” So I studied physics, and the funny thing, was when I… Maybe I talk too much …..
BRUNDLE: No, no. I will…
STEINRUCK: You’ll cut it down.
BRUNDLE: Yeah, and interrupt. But no, just go ahead.
STEINRUCK: The funny thing was - because I was in this little village - the level in the school was so-so, la-la, okay. Then I went to university and my physics was pretty much ok, but my math wasn’t that good. So I went there and we had the first lectures on how to deal with errors and error progression, and all that stuff. And there was the logarithm at some point, ln.
BRUNDLE: Oh, yes.
STEINRUCK: I did know, what ln meant, and after the lecture I went to the professor and said, “There is this ln. Do I need that in physics?”
BRUNDLE: [Laughs] What did he say?
STEINRUCK: “Are you sure you want to study physics?” [Laughter]. At the end, it meant for me half a year of learning, learning, learning, learning and trying to catch up, catch up, catch up.
BRUNDLE: In maths, yes.
STEINRUCKSTEINRUCK: In math, yeah, because my math was really a mess. But yeah, I made it.
BRUNDLE: But that didn't divert you from physics.
STEINRUCK: No. In the beginning, physics was not so much in the focus. The education in the German-Austrian system focusses mostly on math at the beginning because that sets the fundamentals.
BRUNDLE: Ah, I see. Yes.
STEINRUCK: In the first year, we learned about mechanics and geometric optics, a little more advanced than in highschool, but the math is really tough; you sit in the same lecture as the math students. So this is really very theoretical – we called it epsilontics. You demonstrate that there is a solution to a problem. You don't calculate the numbers, but you just demonstrate that there is a solution. I had sort of a delayed start, but at the end it helped me because then I really realized that I have to work hard to achieve something. Then I kept on going because it had worked out and I passed the first exam in the first attempt. The Austrian grade system is 1 to 5, with 1 being the best grade. I got a 4 and was very disappointed, until I realized that only one-third of the people passed.
BRUNDLE: Aha! [Laughs] So yes, very good.
STEINRUCK: And then I said, “Oh! Maybe that’s not that bad after all” because there were really clever people there that participated at the mathematics Olympic games; they were really, really, really, really good. One guy, he really was this mathematic genius type of person. Against him you were a dwarf. On the other hand, I was a normal physicist, so that was sufficient.
Okay. Thereafter, it went well. I passed the exams in time, or even earlier, and then finished after nine semesters. This is one semester faster than the plan was, but yeah, I was running very well and then I didn't want to stop and I also had quite some fun. I also developed my own approach, which I managed to transmit to my kids. You work or you not work – on/off - like a digital function. So when I was at the university, I was working like hell. On the other hand, I grew up in a skiing area, so I also was ski instructor to earn some money, and when I did that, I was partying up to 4:00 in the morning or longer every day. [Laughs] So, one or zero. That worked out really well.
BRUNDLE: Split personality, yes.
STEINRUCK: Split personality, yeah, that’s a way to describe it. Then I attended a lecture by Klaus Rendulic. You might know him. He worked with Erwin Mueller. Rendulic, he is 78 now.
BRUNDLE: No, I don't know him, but I know some of his work.
STEINRUCK: Oh, he was ten years at Penn State with Mueller.
BRUNDLE: Yes. Penn State, yes.
STEINRUCK: Yeah, at Penn State and then he moved to Graz and I attended his lecture. This was on surface science, and was really fun. We had a lab course and in the lab course I did field ion microscopy, hands-on. So we took the pictures and we also did some first atom probe measurements. That was really, really great—time-of-flight atom probe. That just started to come nearly 30 years ago. Then it disappeared, but now it’s really fashionable, coming up again.
BRUNDLE: Definitely coming up again.
STEINRUCK: I decided to do my master’s thesis in that direction. But then Rendulic came to me a week before I was to start and said, “You know, I have a problem. This one coworker, Adi Winkler…” I don't know whether you know him. He was also a postdoc there at that time. “He’s going to leave to become a coworker of Balzers,” the vacuum company, and so I need somebody to work on the other chamber.” However, this was on a different subject, temperature-programmed desorption of hydrogen on Ni(111), but it also sounded interesting. So I thought, “Okay, if the professor says” and I went in this direction.
BRUNDLE: That’s interesting because Steven George started also in surface science the same way, doing temperature-programmed desorption. [Chuckles]
STEINRUCK: You know that Steven and I, we have been at Stanford at the same time?
BRUNDLE: He told me! Yes.
STEINRUCK: Yeah, I told him yesterday. Back to Graz - so I thought, “If the professor tells me this is to be done, then I should do it.” I was not that much focused on field ion microscopy. So I went to do temperature-programmed desorption. I studied the question whether hydrogen adsorption is activated, and when you have an activation barrier, is there normal energy scaling in the adsorption? If you come in at normal incidence, you should have all the kinetic energy available to go over the barrier, and if you go grazing, then the situation is different. The question then was, what happens during desorption?
So I built a setup for doing angle-resolved thermal desorption with a special detector. I think Tatsuo Matsushima in Japan did it roughly at the same time, the same type of experiments. I built a collimator and evaporated titanium on the inside in order to have a pump, and stuff like that. This was my master’s thesis and then I moved on in my PhD thesis measuring the sticking coefficients also in an angle-resolved way, in order to check detailed balance. It was all about microscopic reversibility. For the adsorption process and the desorption process in equilibrium, the rates should be the same? But we don't do an equilibrium experiment and the question was, is what we measure what you would measure in equilibrium or is it different?
BRUNDLE: Yes. This is part of the work that I know about you because of my colleagues Dan Auerbach and Alan Luntz…and I got dragged into the sticking probability field by them as well. So I knew of you through that, not through your current work. So when was that?
STEINRUCK: This was in ’85.
BRUNDLE: And you were where at that point?
STEINRUCK: In Graz. This was still in Graz, at the Technical University in Graz.
BRUNDLE: Still there, yes.
STEINRUCK Everything went really well, so it took me, from starting university until my PhD, only six and a half years altogether. I was really young—I was 26—in the Austrian system with the army and everything.
BRUNDLE: That’s very young, yes.
STEINRUCK: Then I wanted to apply for post-doc positions, but I didn't know with whom I should work, so I asked Klaus Rendulic.
BRUNDLE: And you ended up with the king of thermal desorption in surface science at the time, Bob Madix, right?
STEINRUCK: [Laughs] Yeah! Well, the funny thing was he told me, “Okay, here are some names.” He wrote them down: Dave King, Gabor Somorjai, Bob Madix. I wrote all of them and I got an offer from all of them. [Laughing]
BRUNDLE: Got a note from all of them.
STEINRUCK: Even an offer.
BRUNDLE: Oh, an offer from all of them. Yes.
STEINRUCK: They said, “Come to Liverpool.” Gabor said, “I have a project with Horia Metui,” and then Bob Madix said, “Yeah, come to Stanford.” From the distance, Stanford was the most renowned place, and I looked up what they did and thought, “Oh yeah, this is thermal desorption, this is reactions on the surface. Let’s go there.” This was a stomach decision because I really have to say… If you come from such a small place like Graz – in the group meeting we have been three or four people – you do not really have a clue. Later, I was in the Menzel group, the group meeting with 30 or more people. In Graz, there was a relatively narrow knowledge, very deep but narrow. Thus all these decisions, yeah, were stomach decisions because I didn't know about Somorjai. I didn't know about King too much, either. Nor did I know about Madix, but I just made this decision. My wife Hadwig – we just had married – also supported the decision to go to California. So, I went to Bob, and got along perfectly well with him.
BRUNDLE: So what time is that?
STEINRUCK: ’85 and ’86. So I went there--
BRUNDLE: Did you see me there at all? Was I there then?
STEINRUCK: Yeah. I remember you.
BRUNDLE: Yeah, because I came and spent just a couple of months. We were doing work together, but I bailed out of IBM for a while because there was a tremendous amount of building going around where my lab was. So Bob said, “Well, why don't you come up here?”
STEINRUCK: Yeah, but you did electron spectroscopy, yeah?
BRUNDLE: Yes.
STEINRUCK: But I didn't know what an electron was at the time.
BRUNDLE: [Laughs] Okay. Yeah.
STEINRUCK: I used LEED and Auger, but I had no clue really.
BRUNDLE: Well, I didn't know what thermal desorption was until I met Bob, either. Well, I did know what it was, but I didn't know how it was used in surface science and catalysis. Yeah.
STEINRUCK: So I went there and started and Bob put me on the supersonic molecular beam system. In Graz, I had been doing my adsorption experiments with a very simple molecular beam. You take a capillary array, similar to a channel plate, not with the tilted capillaries but with the straight ones, 90°, and not covered, just the glass. They have a length of 1 mm and a diameter of 20 μ and this gives you a very directed beam, extremely directed beam. So you could measure the angle-dependent sticking coefficients, but it’s a thermal beam, with a Maxwell-Boltzmann distribution.
BRUNDLE: Dan Auerbach was building much fancier things.
STEINRUCK: Yeah, exactly, and Bob Madix also had a supersonic beam.
BRUNDLE: Yes.
STEINRUCK: So I learned to use the supersonic beam and to do the scattering experiments, trapping desorption and direct inelastic scattering. I learned everything there, and it turned out to be really very successful. So I guess I got six papers out of a year. Then I went home for Christmas and I had met Menzel beforehand at a ski meeting. Do you know Dietrich?
BRUNDLE: Oh, of course. Very well.
STEINRUCK: He is very competitive.
BRUNDLE: Oh yes, and he’s an extremely good skier.
STEINRUCK: I wouldn't say extremely good, but just pretty good because he didn't grow up skiing. He was a ski worker. He went everywhere, but for him it was work.
BRUNDLE: I see. Yes. What about you ?.
STEINRUCK: That depends on the reference level. My cousin, Brigitte Totschnig, competed at the Olympics and was second in Innsbruck, 1976, in downhill. So I’m not really good on that level, but I’m pretty good for somebody living in Germany, on the flatland. Menzel liked that I was a good skier and he liked talking about science with me. In the chairlift we talked and I said, “I go to the States now, but if I come back, can I call you?” Then I called him. I wrote a letter and called, this was the time. There were not so many people doing physics, so the job situation was great, and I also applied with Karl-Heinz Rieder, Volker Dose, Edmund Taglauer and Hajo Freund. Do you know them?
BRUNDLE: Yes, yes. All of those.
STEINRUCK: And [???].
BRUNDLE: Yeah.
STEINRUCK: I got five offers! [Laughs] It was great, yeah. With Menzel, I had the impression, he was having a great lab. Karl-Heinz and Hajo were moving to new places and I realized that with a professor who moves, you built up his lab, and this was not my intention.
BRUNDLE: Very insightful, yes.
STEINRUCK: And the other thing was Munich. Munich is two hours from where I grew up, so I said, “I go to Munich,” which again turned out to be a very wise decision. Menzel said, “Okay. You can do TPD.” I guess, he did it best in the world concerning signal-to-noise ratio and stuff like that. “Or, I have this synchrotron machine that doesn't work.” They had set up a toroidal electron energy analyzer where you could measure at electron emission angles from zero to 90 degrees simultaneously, and there was a delay line detector at the end. A postdoc before me built this machine, but he didn't get it to work. The luck for me was, he did 95%.
BRUNDLE: So even though you went to Menzel, you were still setting things up. [Laughing] Which you wanted to avoid! But you didn't, yes.
STEINRUCK: Yeah, but the machine was there and he said, “You have to get it running.” Yeah, and then I learned what an electron is. [Laughs] From Eberhard Umbach, I took his desk. He was moving to Stuttgart, and I had long discussions with him. Eberhard is very nice and clever guy… Do you know him?
BRUNDLE: Of course, yes.
STEINRUCK: Also of course from Stanford and from electron spectroscopy. He also did his postdoc there.
BRUNDLE: So yes, I know him very well.
STEINRUCK: He became an extremely good friend of ours, so we know each other. Our kids know each other, so that’s really nice, and we meet regularly. He taught me a lot about electron spectroscopy. I was drilling holes into him when we were going to a conference three hours by car and there was all this satellite stuff and also screening, spin-orbit splitting and charge transfer. So I learned many things like that. In the Menzel lab, there was a very high level on understanding, because of Menzel, I got to know all these details about photoemission. I really learned from many, many, many discussions.
BRUNDLE: Menzel spent two brief sabbatical times—not a year, but six months—with us in San Jose—myself, Dan Auerbach, Paul Bagus.
STEINRUCK: Yeah, I know, I know.
BRUNDLE: So yeah, we also had lots and lots of discussions.
STEINRUCK: Yeah, and that was really very helpful because I think, if you work with a method, you really should go to the very, very, very basics. They don't go away then. You might forget about details, but the essentials don't go away in your stomach, gut feeling. Okay.
Then yeah, I managed to get this machine going. So we had beamtime at BESSY I half a year later and I never had worked at a synchrotron before. Luckily, we could set everything up quickly, and tested it and it worked from the very beginning. This machine was very nice because it would measure simultaneously from 0° to 90° valence photoemission spectra. I started studying adsorbates, using symmetry selection rules and did band structure studies. We measured the band structure of benzene, ethylene, and it’s really amazing. For ethylene, you have a dispersion of 2 eV of the valence levels and yeah, that’s still, I guess, state-of-the-art. Nobody did it better since then for hydrocarbons. Hajo Freund also did some great work, especially on CO on Ni(110).
BRUNDLE: Yes.
STEINRUCK: You know this work on Ni(110).
BRUNDLE: Yes.
STEINRUCK: This is an extremely nice paper and we did more or less the equivalent for the hydrocarbons.
BRUNDLE: Yes. I came from a gas phase ultraviolet photoelectron spectroscopy background, so like you didn't know what an electron was for a long time, I had no idea what a band structure was until I went to Bell Labs as a post-doc.
STEINRUCK: And there was the book by Roald Hoffmann. You know it? The title is A Chemist’s View of Bonding or something like that.
BRUNDLE: Oh yes, yes. Oh yeah, of course.
STEINRUCK: And this is extremely nice and helpful. So yeah, I did that. That worked out very well. Then, at the end of my time in Munich I started another direction, which I didn't pursue further because I couldn't take the machine with me when I left. The method, we started was photoelectron holography. You know J.J. Barton.
BRUNDLE: Yes.
STEINRUCK: He introduced that method conceptionally and we did the first experimental proof that it really works. This was possible, because our machine would not only work in the valence region, but also in the core region at kinetic energies from 100 to 500 eV, where you have multiple scattering. We did the measurements. Barton also introduced a multiple-energy averaging technique. If you use only one kinetic energy, you have always the true real space image, but then you also have artifacts. The artifacts average out, if you average different images measured at different energies kinetic energies, that is, wave lengths. Barton introduced the procedure and we applied it. We measured the data and it worked. However, I also realized the weaknesses of the method, because its sensitivity decreases with the distance of the imaged atom to the source. Upon electron emission from an atom you have a spherical wave. The further you go away, the less intensity you have left, and therefore you see the next neighbors and the next-nearest neighbors, but then is fades.
BRUNDLE: Not after that. It’s a short range, yes.
STEINRUCK: Also, if you have inequivalent atoms, you’re lost. So it’s nice for sulfur on Ni(111). We demonstrated that we could reconstruct the threefold adsorption sites people knew beforehand. One other advantage is that it also works for non-ordered adsorbate systems because you don't need long range order.
BRUNDLE: You don't need long range order, yes. How did you move on ?
STEINRUCK: In 1992, I did my habilitation. At that time, my wife and I already had our two kids, two boys, Hans-Georg and Philipp. The next year, the kids were still small, three and five, I said to my wife, “Okay, I would like to go to the States again.” I knew Ted Madey and approached him “Okay, Ted. Can I come next summer for a sabbatical?” and he said, “Of course.” I also got to know him on a ski conference. Ted was learning to ski on a Symposium on Surface Science in Obertraun, Austria !
BRUNDLE: Yeah. I was going to say I didn't think he was a skier, but he just…
STEINRUCK: No, not at all. It was really funny because Ted Madey, Bob Park, and I think also Dan Auerbach—I’m not sure about Dan—were beginners and the three were in the group. And you know Bob Park, I think, very good.
BRUNDLE: Yes!
STEINRUCK: Yeah. He was extremely sportsman.
BRUNDLE: Oh yeah, and exceedingly competitive.
STEINRUCK: Yeah, exactly.
BRUNDLE: Probably more so even than Dietrich Menzel. [Laughs]
STEINRUCK: Yes. He was trying to do everything with brute force, and the ski instructor said to him, “Ah, you don't have any talent. You should do some sports. Otherwise you’ll never learn skiing!” [Laughter] Bob’s reaction was that at -15° he went outside running around the building one hour to demonstrate to the ski instructor that he was in good shape and a sportsman. [Laughing] It was really funny.
So I went to Ted in the summer of 1993 – he was already at Rutgers, and we did some nice work on platinum encapsulation on TiO2, and on how a CO gas-phase changes the wetting behavior of Pt on TiO2. Both papers have more than 100 citations now, so that was really a fantastic summer.
And I got to know Ulrike Diebold at that time, because I was taking over her chamber, when she moved to Tulane. We had one week overlap and she said, “Okay, this is the machine and these are the problems”. Ever since then I know Ulrike really well and we stayed friends over the years. We are both Austrians, and there are not so many Austrians around.
BRUNDLE: Well actually, there seem to be a lot because two of the award winners are Austrian! I mean Marcus Valtiner is Austrian, too, and also comes from a small town.
STEINRUCK: Oh, yeah. Marcus is also Austrian, yeah.
BRUNDLE: Okay. We ought to move on a bit here, I think.
STEINRUCK: Oh, yeah. Then I can speed up. During my stay at Rutgers, I got a job offer to in Würzburg and became professor in experimental physics at Würzburg University. There, I applied for money for a molecular beam system and for an XPS system - both proposals were granted. This was, when I started doing XPS as a main method. My ARUPS machine stayed in Munich, I still could use it, but not to the extent I had before. We did several projects at the same time. In one, we measured band structures of ultrathin metal layers, e.g. monolayers of copper on different substrates, and tried to understand it beyond the d-band model. The latter relates the d-band center of a metal to its chemical reactivity. My idea was that there must be some effect of the symmetry of the d orbitals, which is completely ignored in the d-band model. We did indeed get quite some understanding. Yeah, then four years later, in 1998, I moved to Erlangen where I am now.
BRUNDLE: Is that when you started getting interested in liquids? And why?
STEINRUCK: Not at that point. It was funny because at the same time I had also the offer to become the successor of Comsa in Jülich.
BRUNDLE: Oh, okay! Yes.
STEINRUCK: So there were two offers, Gerd Wedler’s succession at the University of Erlangen-Nürnberg and George Comsa’s position at the Research Center Jülich. The offers were pretty comparable. At this time, I really liked to teach, so I wanted the contact with the students. So I decided to go to Erlangen, and this is when I moved from physics to physical chemistry. So I converted to be a chemist. From then on, my students are mostly chemists. Over time, I became more and more brave and also addressed larger molecules than hydrogen, CO or benzene. We started working on porphyrins, and then with the ionic liquids, in 2005.
BRUNDLE: Far removed from hydrogen scattering. [Laughter]
STEINRUCK: Right. The most difficult thing was pronouncing the names of the molecules.
BRUNDLE: Well, I’m a chemist by background, but I always hated organic chemistry. I couldn't recognize the structures when they were written the other way up, which is a problem. [Laughs]
STEINRUCK: The story, how I got started on ionic liquids is quite typical for science. So, Peter Wasserscheid, who is a chemical engineer and is one of the godfathers of ionic liquid science, we have our offices on the same floor; he really is a very nice guy and became a close friend over the years. So we started talking and discussing on the hallway and ...
BRUNDLE: To interact, yes.
STEINRUCK: and finally in 2005, I said, “Okay, let’s be brave and put this liquid stuff in the UHV chamber”. We were sort of hesitant. Well, what happens to the chamber? This was an ESCA machine from VG.
BRUNDLE: ESCALAB?
STEINRUCK: ESCALAB bought in 1990 and this was our oldest machine. I inherited it from my predecessor, and I said, “Let’s try it with this machine”. It immediately worked out. We got very nice XP spectra. They look fantastic. Have you been in my talk yesterday?
BRUNDLE: No. I was somewhere else; I couldn't go to it.
STEINRUCK: Oh, so you know a little about ionic liquids?
BRUNDLE: Only a little.
STEINRUCK: So we had this ionic liquid and then we dissolved a platinum complex in it. If you want to have a reaction of gases from the gas phase above the liquid with the dissolved complex, then it would be good if the complex would be enriched at the surface because then the reactants have to diffuse only a very short distance. So the question was, is the complex enriched at the surface ? We found that this platinum complex was extremely enriched. So we measured for three weeks, submitted a Paper to Angewandte Chemie, and it was accepted right away. This made us confident. [Chuckles]
BRUNDLE: So I’m intrigued. What was the pumping system in this?
STEINRUCK: Just a normal UHV chamber.
BRUNDLE: Which is what? What was it? It’s probably oil diffusion pumps, was it?
STEINRUCK: No, we changed it. Originally, it had diffusion pumps, but we changed it all to turbo pumps. The ionic liquids were similar to Santovac, vapor pressure-wise. Yeah, we measured and it worked. Then, we found silicon contaminations from the grease of the glassware used in the synthesis, and then we talked to the synthetic people—they were next door—and convinced them that we have to avoid that. They changed to glassware without any silicon grease and all of a sudden the ionic liquids were clean. We started to do systematics, studying ionic liquids with different chains attached to imidazolium cations. We put on short chains, medium length chains, and long chains to systematically investigate surface enrichment effects. There were some two XPS papers before, but they only measured XPS at one emission angle. We now did angle-resolved XPS, from 0° to 80° electron emission angle. And indeed, we found strong surface enrichment of longer alkyl chains. It went really smooth. Everything, we knew from surface science, we could now apply to these liquids. So we did, and this was really easy because we knew how to proceed. Some of the other groups in the field came from a completely different background, but for us everything was the normal way of doing things. We varied the chain lengths of alkyl chains, introduced functional chains, changed the anions, studied the interaction between different anions and cations, and looked for the chemical shifts in XPS. We compared them to those in NMR to see what can you learn about interactions from NMR and can we correlate it? We measured the macroscopic surface tension and correlated it with the surface composition, and everything worked. Then we realized that we can evaporate ionic liquids. We could use normal organic evaporators and studied the growth of ionic liquids on metals and oxides, and the molecular orientation in these layers, and also the wetting behavior. Everything we knew from the surface science could be applied. Then we studied reactions in ionic liquids. We were the first to do it. It was really simple, but rewarding!
BRUNDLE: So how many years has that been going on now?
STEINRUCK: 11 years, and we have like four to five papers per year.
BRUNDLE: In this area.
STEINRUCK: Yes - initially there were only a few groups working using a surface science approach. We entered a new community, and people were very interested in our results. Then it’s more or less a little autocatalytic. It’s so much simpler in a new area than in a classical one. However, we continued our research in classical surface science. We use synchrotron-radiation for in situ reaction studies. We also do method development in that area. We routinely measure XPS spectra with a measuring time of 1 to 10 seconds per spectrum. We also developed a setup to measure with a time resolution of 500 microseconds. Then you have to use a pulsed beam because you have to repeat the experiment all the time, because in 500 microseconds there are not enough count in a single spectrum [?]. But if you repeat with the pulsed experiments, you can average and get reasonable statistics. Then you can follow reactions like CO oxidation at much higher temperature than normally. We still do that. We also invented isothermal XPS. You’re a chemist, so you know reaction kinetics typically are done by isothermal experiments. In surface science, because you cannot measure fast, people typically do temperature-programmed work. Now we can work in a synchrotron, and measure really fast- so we can--
BRUNDLE: You can do that now, yes.
STEINRUCK: Yeah. We can do it fast. Slow is not a problem anyway, so you can span large time windows for the whole reaction, from fast to slow. This means you can follow the reaction over a reasonable large temperature window, and then you can do an Arrhenius analysis; if you were to only cover 5 or 10 Kelvin, then the Arrhenius analysis would be completely arbitrary.
BRUNDLE: Yes.
STEINRUCK: But now we can do that, and isothermal XPS and works very nice for reactions where you can create conditions where the kinetics is simple. If the kinetics is very complicated, it remains complicated. But if you work with excess of one substance, then you get a pseudo first-order reaction and then you can determine the activation barrier from the Arrhenius analysis.
BRUNDLE: So that brings us up to now. Another thing I’d like to ask is how long have you been involved with the AVS? When did that start?
STEINRUCK: I’m not so much involved with the AVS.
BRUNDLE: But you come to meetings.
STEINRUCK: Yeah, I come to meetings, but not that regularly. The problem was a little that…
BRUNDLE: That’s even more impressive. Then you get the award, but you're not a regular attendee. [Laughs]
STEINRUCK: Yeah! I think maybe it’s my fifth conference over my career.
BRUNDLE: Over how many years?
STEINRUCK: Since my post-doc time, so 30 years. The problem was a little that in the middle of my career, about I took over quite some administrative duties, so I was dean for two years and then I was vice president for my university for six years.
BRUNDLE: Ah, okay. So no time for conferences in the US. [Laughs]
STEINRUCK: Exactly. I made a decision: no teaching and conferences only when I was invited, during my time as vice-president—this was from 2006 to 2011. In 2006, when we also started the ionic liquid activities, I initially wasn’t invited that often, so I didn't travel that much. The group was running; it was running well and I worked really hard. Our kids were already out of house at that time, which helped. Also, my wife Hadwig is very patient and supportive, which helped even more. Yeah, I decided not to go to meetings too often. I was in the US every other year, now it’s twice a year typically. And then the invitations came—at that time mostly from the ACS meeting, because the ionic liquids are very interesting for the chemists, and the physicists are a little more hesitant.
BRUNDLE: Yeah. That’s where Bob Madix ended up as well. I mean he was always a big supporter and involved in AVS, but gradually he switched to ACS and his own background of people once surface science became more accepted by ACS because it wasn’t originally.
STEINRUCK: Yeah, yeah. That is very much--
BRUNDLE: That’s why it had a home in AVS.
STEINRUCK: Yeah, and I have to say this meeting is great - you have a much, much broader audience here.
BRUNDLE: Yes.
STEINRUCK: I can go to so many sessions without looking at the program and just listen. I find it entirely interesting—very different to the ACS, where there typically are only a few interesting sessions.
BRUNDLE: Yes. That’s how I got involved first—much smaller meetings then, but they were just everybody, physicists, chemists, electrical engineers, all kinds of people, and I had never been to a meeting like that. That’s way back in 1974, by the way. It was in New York, I remember. [Laughs] I was very impressed and joined. Well, they gave you a membership for a year and I got the journal because of that, and that had 90% of all the surface science that was being done at that time. And I’ve been with them ever since. Okay. So I think we’re pretty much towards the end here. You’ve already answered one question that I didn't ask. You have two children, right?
STEINRUCK: Yes, two boys.
BRUNDLE: How old are they?
STEINRUCK: 29 and 27. Both are off my payroll.
BRUNDLE: [Laughs] Are they in science?
STEINRUCK: Funnily, the older one yes, he is a post-doc with Mike Toney at SLAC.
BRUNDLE: My goodness—who was a colleague of mine when I was at IBM.
STEINRUCK: Oh, really? He is there since two years and he’s doing battery research. He’s a hard x-ray person, so he got his PhD in hard x-ray scattering and yeah, now he is there and having a good time. At the moment, he’s in Brookhaven measuring. And the younger one studied law. [Chuckles]
BRUNDLE: Ah! So you do have legal in the family! [Laughs]
STEINRUCK: Yeah, and he’s going to be a lawyer. He’s now in the last part of his education. In the German system, if you become a lawyer, after your state exam you have to do sort of an internship for two years where you first work with the judge, then with the state attorney, then with the administration, then in a law firm, and he is in the middle of that.
BRUNDLE: Yeah. And one final thing I always like to ask is you’ve been through all this all over the place and changing direction of what you're doing based on what you observed and people you’ve talked to. What advice at this point in time would you give to a young person? It might be different in the US than in Germany because funding is a lot harder here now. But if they were partway through their PhD but not sure what they’re going to do, what would you suggest? What should be their approach?
STEINRUCK: Hmm. The first thing, I think you have to work very hard. That’s the only way because there are so many bright people around. Normally, you're not brighter than the other people, so you have to work hard. Then you have to be very critical to yourself.
BRUNDLE: Very critical to yourself?
STEINRUCK: Yes, because it’s…yeah. This is because science is very much about judging work, other people’s work, and in turn you will be judged. So if you are self-critical, then you have already passed the first level of judgment…
BRUNDLE: I see. Yes.
STEINRUCK: …because if not, somebody else tells you what you do is nonsense. So that’s something which is, I think, important.
BRUNDLE: So hard work, self-critical.
STEINRUCK: Yeah. My personal experience also was to talk to people and listen to them, but then make your own decisions.
BRUNDLE: Yes. I think that’s a good way to go, yes.
STEINRUCK: So we are done ?
BRUNDLE: It’s all right. Okay, so I think we’ll finish at this point. I congratulate you again on your award.
STEINRUCK: Thank you very much.
BRUNDLE: It will be given tonight at the award ceremony, and then the reception afterwards to celebrate that.