Awardee Interviews | Dietrich Menzel - 2012 Gaede-Langmuir Award - Interview

Dietrich Menzel

2012 Gaede-Langmuir Award

Interviewed by Paul Holloway, 2012
HOLLOWAY:  Good afternoon. My name is Paul Holloway, and I’m a member of the AVS History Committee. Today is Thursday November 1, 2012. We’re at the 59th International Symposium of the AVS in Tampa, Florida. Today I have the privilege and pleasure of interviewing Professor Dietrich Menzel from the Fritz Haber Institute, Max Planck Society and the Technical University of Muenchen. He is the 2012 Gaede-Langmuir Award winner, and his citation reads, “for major ground-breaking and sustained contributions to the comprehensive understanding of the energy transfer processes influencing the physical and chemical behavior of atomic and molecular species on metal surfaces.” So congratulations, Dietrich. A well-deserved honor, and I’m very pleased that you received it.

MENZEL:  Thank you very much. I’m pleased, too.
HOLLOWAY:  Can we begin by you giving me your city and country of birth and birthdate?

MENZEL:  Yes. I have been born in Marienbad. It was named thus at that time. Now it’s called Mariánské Lázně. It lies in what then was Czechoslovakia, up to 1918 Austria-Hungary- that part of old Bohemia which was inhabited by Germans- and now it is Czechia, and I lived there to 1946 until the Germans on the grounds of the Yalta agreement were moved out, I think three million of them, and then I lived in what is West Germany. I was born on the 27th of February, 1935.

HOLLOWAY:  You’re just a young spring chicken, then.

MENZEL:  Yes, exactly.  [Laughter]

HOLLOWAY:  Maybe we could continue with you telling us something about your educational background.

MENZEL:  Well, I went to school in a small town on the Rhine close to Frankfurt, and I got my what we call Abitur,  the exit exam of gymnasium, in 1954. And then I went to study chemistry in what then was Technische Hochschule (TH), now the technical university of Darmstadt, which is also around there, and I did real chemistry and I then specialized in physical chemistry. I got my masters, what we call Diplom, got the degree of Diplomchemiker with work on pitting corrosion.

HOLLOWAY:  Corrosion of steel?

MENZEL:  Yes, of iron, but that’s this type of corrosion, ”pitting corrosion” where very small but deep going holes, which can be very, very dangerous for the structure of materials, and there are quite interesting phenomena taking place there. But after that, I switched a bit and did a PhD in very basic catalysis, namely the simplest possible reaction that exists, the ortho-para hydrogen conversion, where you go from a hydrogen molecule to a hydrogen molecule, and you only have a label (from nuclear spin symmetry)  that can show you that something has happened in between. That took place in an Institute of Physical Chemistry where the professor, his name was Witte, was mainly interested in x-ray diffraction, and I was working with a young postdoc you would say who was interested in basic catalysis, and so I did work on this ortho-para hydrogen conversion on platinum and platinum-gold alloys in dependence of the pretreatment, we called it, which really means in dependence of what was adsorbed on the surface. At that time, this was 1959, we didn’t know what that was, but we knew we could change something. And in fact this got me interested in the basics of adsorption and of how one would go about getting information on what is really on the surface. So when I was looking for a postdocship I looked at the literature and I found the only instrument that would tell you what really is on the surface at that time was the field emission microscope. And of course, this also meant that essentially you were confined to doing tungsten. This was really the tungsten era of surface science..

So of course you look who is most prominent, and of course most prominent was Erwin Mueller at Penn State. So I thought about writing to him, but then my professor who was in a different field but who was trying to help me to find the right place, he had a visitor from the University of Chicago, Lothar Meyer , and he told me to talk to him. And we talked, and I said, “Shouldn't I write to Erwin Mueller?” and he said, “I would not advise that. He is an extremely difficult person. But I know somebody who is as good, and is not quite as difficult,” although it turned out he was difficult, too, because that was Bob Gomer at the University of Chicago. So I wrote to Bob and he accepted me, and I arrived there in September 50 years ago—September 1962 I arrived in Chicago, and I stayed there close to two years. We got along surprisingly well because most people had trouble at that time with Bob. He was a demanding person. But I had no problem whatsoever. Somehow we respected each other. [Chuckles]  And so yeah, we did very nice work, which was sort of the basis of many other things, the so-called MGR mechanism, the Menzel-Gomer-Redhead mechanism of electron-stimulated desorption, stems from that work.

HOLLOWAY:  Let me back up and make sure. You got your PhD from Darmstadt?  [Yes.]  And what year was that?

MENZEL:  That was ’62. In the beginning of ’62 I got the PhD in February, and then I looked around. I had a sort of assistant position, so I had time to look around. And it developed that I would go to Chicago, but then they couldn't take me immediately, so I went in September.

HOLLOWAY:  So you immediately jumped into the interaction of electrons with adsorbed molecules on a surface?

MENZEL:  Well, this a bit more complicated. Bob had not done exactly that before. The argument was: he had looked at field ionization and field desorption also, and the point there is that when you apply a very high electric field to an adsorbate on the surface, and its ionic state crosses the neutral state under very high field conditions, that can lead to desorption. So he looked at this effect. But then he argued you should also be able to do exactly the same by an external excitation. And at that time, of course, photon sources with sufficiently high energy and high intensity did not exist, there was no laser, there was no synchrotron radiation, there was nothing. There was just mercury lamps. And so that would have been difficult, but we decided okay, let’s try electrons. At least in the dipole part of the interaction they essentially behave like white light. And so we decided to do it with electrons. And the fortunate thing with electrons is, you know, the source is small. We worked at that time in sealed-off glass apparatus, six centimeters in diameter, that everything had to be put in there. Then it was baked and sealed off, and then the whole thing, like 20 centimeters long, six centimeters in diameter, was put inside liquid hydrogen. That gave you a much better vacuum than you could get anywhere. 10-15 millibar you could extrapolate from the contamination rate. But of course if something didn’t work, the whole thing had to be done again.

HOLLOWAY:  And so you had to have a good glass blower.

MENZEL:  No, we did it all ourselves.

HOLLOWAY:  You did it yourselves, good!

MENZEL:  Bob was an excellent glass blower, and there was a graduate student at that time, you may know the name, Lanny Schmidt. He was a graduate student while I was a postdoc. And he also was an excellent glass blower. But I had to do my work myself, and I was not a good glass blower—it looked always ugly, but it worked, so that was sufficient. And so to put that all in there, you had to have a very small source, and you could build a little electron gun very small-less than 1 cm- just out of three electrodes made of platinum foil, so that was perfect. And the gas which you used for adsorption was put inside the tube before sealing off, and then there was a little platinum platform inside which when you cool down the whole thing was cooled first. So there was a tubing through which the liquid hydrogen went first to the supports of that little platform. So the whole gas that you had put in, say 10 millibar of oxygen or CO, was condensed on there like white snow, a little layer of snow. And then the whole thing was cooled down, and there was a sort of primitive collimator, so by heating  of this platform you could cause sort of molecular beam dosing of the tip, which was there as the main instrument and which only consisted of a tungsten wire loop and a welded-on field emission tip. So that was the whole machine.

HOLLOWAY:  But I would imagine if you’re cooling it with liquid hydrogen, there are some stories about that.

MENZEL:  There are some stories about that. Yeah, yeah, indeed. We had to have an exhaust that let the hydrogen gas outside, and of course the space between the Dewars had to have pumping, so we had a rotary pump on the floor, and we had a hydrogen gas duct running close by and going up. And one day I noticed that the rubber tubing that let the hydrogen into the main metal tubing had come off on the floor, and two meters apart was a running rotary pump. And nothing happened because the hydrogen is so fast up there. But you know, I got scared [laughs].

HOLLOWAY:  I would have been scared very much as well.

MENZEL:  And my record to have the tube working—You could keep it in the liquid hydrogen as long as everything worked, so you wanted that as long as possible, and my record was six weeks that I could keep it cold and work with it, because you had to dose it with adsorbate, you had to define the coverage, which is done by measuring a Fowler-Nordheim plot and calculating the work function. And then you had to bombard with electrons of a certain dose and energy, and then you had to look again. So that was the simple measurement, and it took time, but it worked. We got nice results, and we put together a model. At the end of the work Bob knew from some meeting that Paul Redhead in Ottawa had come to a similar conclusion about the model on grounds of quite different measurements.

HOLLOWAY:  He was primarily interested in ion gauges, I believe.

MENZEL:  Yes. And that’s the nice thing. That’s why I like the Gaede-Langmuir Award. You know that Gaede is the vacuum side and Langmuir is the surface science side, and they really were intertwined. You needed surface science in order to improve vacuum technology. You needed vacuum technology, good vacuum, well defined vacuum, in order to get good surface science. So that made this connection. So he (Redhead) came from that side and did a totally different measurement, but he only looked at what came off, the ions, and we looked at what was left behind, so we had a total effect. But saw essentially similar dependencies on the parameters of the thing, and therefore we came to a quite similar model, and it was published roughly at the same time, so that’s why it’s called MGR now, because we were independently coming to the same conclusion.

HOLLOWAY:  That’s a remarkable story. But the Menzel-Gomer-Redhead model was the premier model and stood for all these years.

MENZEL:  Yeah, and it’s still helpful. Of course we know that things are more complicated. You can have many variations. At that time, for instance, we only thought about transitions to states which by themselves are repulsive so that things fall apart right away. Now we know that all you need is you go to a state where the potential energy curve in the Franck-Condon  region where the transition takes place has a slope. It doesn’t matter whether it’s repulsive or attractive, because if it’s attractive things run together, or for instance if the dimension on which you looked is the bonding to the surface, then of course the particle  moves towards the surface. But eventually it bounces and just turns around.

HOLLOWAY:  It bounces against the repulsive force and turns off.

MENZEL:  So it’s not a change of principle of the thing. It’s the details which have to be changed.

HOLLOWAY:  I noticed in your lecture that you didn’t name names—you didn’t call it the Menzel-Gomer-Redhead model.

MENZEL:  Well, this is not important. Especially I would have to go through many names, and then you have to think about what was really original or not. There’s the Antoniewisz (which should really be called the Gadzuk model) the original model assuming attraction in the excited state. Of course there’s also Knotek-Feibelman, which was very interesting to get things moving, especially since it was put forward with very strong emphasis. But I think there is not a real system which really works according to it. I mean the original idea of the Knotek- Feibelman model was that by looking at what is desorbed according to this effect, you would sort of be able to project out the ionic part of a bond, and that doesn’t work. I mean this is simply not the case. But it was very important for further development. And we also found about the same time that excitations which start with core levels are also very strongly inducing reactions, desorption especially. But we explained it essentially in a somewhat broadened MGR model. And so if you don’t take the separate steps too seriously but look at the main thing, you have a semi-classical problem where you have a quantum mechanical primary excitation, and then you have a quasi-classical evolution, which then can also again be terminated by a second quantum transition -   the excitation jumps away so the particle falls back to the ground state. So you have a picture which is conceptually helpful, but if you want to do good realistic calculations, then of course you will not have a particle moving in the semi-classical potential, but this will be a wave packet, and the wave packet will be distorted by the interaction with the substrate and things like that. So this you can refine more and more, and especially now since we have access to calculations of very complicated potential energy surfaces, we can really follow the movement of the wave packet on the potential energy surfaces. So there have been incredible advances in the last 20-30 years.

HOLLOWAY:  One of the principles of the Knotek-Feibelman model was a two-electron process giving you charge both on the molecule that is coming off the surface and the atom remaining in the surface. Is that correct?

MENZEL:  Well, the basic idea was that, yeah, you had to get rid of at least two electrons because he wanted to use it for cases where you have essentially O two-minus (O2-) ions in the ground state, and you know that O plus (O+) comes off. So you have to get rid of at least two electrons, in fact three to get the total charge transfer. So he needed essentially an Auger satellite, an Auger process in two steps. And this is not a very probable thing, but of course the primary excitation of the O two-minus by ionization of the counter ion, the metal cation, that certainly plays an important role. There’s no question about that. It’s just I would describe it a bit differently. But that’s not so important. If you look at the development, the discussion around that and the scrutinizing of the detailed processes was very important to clear up things further.

HOLLOWAY:  Yeah, for example space processing or semiconductor processing, even real-world production processes rely upon that fundamental science.

MENZEL:  Oh yes. Mainly device fabrication where you make photo masks and things like that. These are all connected problems. And on the other hand, radiation damage is connected. There, for instance, we now know and most people agree that the most important processes in radiation damage in biological materials is caused by slow electrons, very slow electrons, because they can attach, and they are created by any sort of radiation. So there the MGR idea is not so helpful. Or you can twist it into agreeing…[chuckles]  But still, I mean it’s just the concepts that evolved, this was the important thing, I think.

HOLLOWAY:  Those were real wild days in surface science.

MENZEL:  These were. Especially this time in Chicago, this is what I call the heroic times of surface science. Really, you had to try hard – now you just go around in the exhibition and see what you need to buy. We had to do everything ourselves. Even later when I was back in Darmstadt starting my own research and wanted to do it in metal systems, I had to do my own heli-arc welding.  [Laughter]

HOLLOWAY:  Were you a better welder than a glass blower?

MENZEL:  Hmm, well, I would say roughly the same thing—I got it to work.  [Laughs]

HOLLOWAY:  Got it to work. That’s the most important.

MENZEL:  Not that it would have been able to compete with the professional stuff.

HOLLOWAY:  So what year was it when you went back to Darmstadt?

MENZEL:  That was ’64. Then in Darmstadt I started two things. One thing was something which had come up during my PhD already, because the way one measured the ortho-parar hydrogen composition was with a hotwire cell where you use the difference of the rotational heat capacity of the ortho-para mixture because the ortho hydrogen  has the 1-3-5- rotational excitations and the para the 0-2-4- excitations, and there is a range of temperature where the heat conductance due to that is very high, the difference of them, and that’s what I used in my PhD to measure the change in ortho-para hydrogen composition during reaction. And it turned out that there was not simply only this effect of this specific heat, but there was also something that had to do with the surface of the hot wire, not just with the capacity of gas conducting heat away. And this must have had to do with the transfer of energy when a body collides with a surface. And this is described by the energy accommodation coefficient. And it turned out that there were no good measurements on that. So one thing was I wanted to measure real good accommodation coefficients, and the other thing was I wanted to continue what I had done in Chicago, but now somewhat go along the line of Redhead, only that I wouldn’t want to measure just all the ions coming off—total ion count—but I wanted a mass spectrometer. And that was not an easy thing at that time to get a mass spectrometer that you could put in a little ultra-high vacuum (UHV) system. I got one. GE had one, a 90-degree deflection machine which I got by complicated ways. I had to play some tricks. In that time you couldn't just order something that worked. And I worked on that. So these were the two lines I followed in Darmstadt.

            Then in ’67 I got my Habilitation  and became a “Dozent” (something like a lecturer), so  I had a position. But in ’69 I got an offer from the what then still was T H Muenchen; now it’s the TU, the  Technical University of Munich. In fact this is interesting, too. At the TH Muenchen there was one physical chemistry institute which was led by a well-known electrochemist, Gerischer, and he had a young Dozent whose name is Gerhard Ertl (Nobel 2007), and in ’69, Ertl got an offer of a chair in Hannover. And so Gerischer was looking for somebody who could continue the line of work which Ertl had started, and since I had  already  my Habilitation, he upgraded this position a bit, and I went there. But half a year later Gerischer said, “I am going to Berlin to head the Fritz Haber Institute,” and Ertl was in Hannover, “and why don’t you come along? I’ll give you a group leader position there. That’s perfect.” I said, “No, I just arrived in Munich. I want to stay in Munich,” so he said, “Okay, you’ll have to see where you can stay if you are alone.” And so I stayed. In fact for a while the chair was unoccupied, so I took over all the courses and the exams, etc., but then we had a new boss.

            And then I had big luck. You know, the kind of research that I did was more and more physics, less chemistry. The chemists usually said, “Oh, what’s that good for?” because that’s much too principled—a question of principal interactions. There are no classes of different compounds, etc., which you would go through. This is not really nice for a chemist. So at that time it happened that the physics department of the same university, which was at that time and I think even now still considered one of the top physics departments in Germany, had decided they wanted to start surface science. They were strong in nuclear physics. There was Mößbauer,   there was Maier-Leibnitz . They were also strong in semiconductor physics; now they wanted surface physics. So they looked around and there was a theoretician, a very good theoretician who had become interested in surfaces, Wilhelm Brenig, a very well-known theoretical nuclear physics man who wanted to convert, and he liked my work and pushed that they should take me. So I got an offer, and at the same time I got an offer for a directorship in the Max Planck Institute in Garching  for plasma physics, which had a department of surface physics. Very good department, actually, but which of course had the mission to do the surface physics necessary for the fusion reactor. And so I had these two offers: University and Max Planck. Max Planck was much better in many respects, but Max Planck  required that I would at least do 70% in fusion-oriented research, while at the University I was totally free. So I opted for the University, and then in ’73 I got my chairin the Physics Department—I switched departments.

HOLLOWAY:  So you changed spots, so to speak.

MENZEL:  Yeah. I also changed locations, and I had it nice—That was a new chair. That was a good time. There was growth in universities. And I was very lucky. When I started out, the hopes to ever get a chair were dismal. There were about 50 people waiting for one chair. And there was this nice story. There was a physical chemistry, the Bunsen meeting in Germany. It’s the physical chemists meeting, and there was this meeting, and I went with four or five young colleagues, and we walked along the street, and in front of us walked four well-established old professors of physical chemistry. And we walked behind them. And then there came a taxi rushing from behind, and we heard it and jumped to the side. The old guys didn’t jump to the side, but the taxi just was able to brake behind them and slid. And then one of my colleagues said, “Oh, what a pity.” [Laughter]

HOLLOWAY:  We could have created more chairs, right here!  [Laughter]

MENZEL:  Ah, yes! So that was the situation in the ’60s, while in the ’70s there were new chairs everywhere, and so I got a new chair. I got startup money, and this was a good time.

HOLLOWAY:  In this timeframe, you were looking at what was remaining on the surfaces and some of what was coming off the surfaces. How did Auger and XPS and those analytical techniques come in?

MENZEL:  Okay, let me make the transition. By that time, when I went to Munich, it had already become clear that you had to really do a better job in definition of what you have, and at that time we were able to prepare single crystal surfaces. We had LEED. And when I came to Munich, there had been a LEED apparatus left behind by Ertl, who had worked on this there. And then there was Auger spectroscopy in the late ’60s, and so I started to work on that. And like I told yesterday (in my acceptance talk), in ’71 I attended my first AVS meeting in Boston. I heard Dean Eastman, I said immediately we have to do that, we have to do photoelectron spectroscopy on those well-defined surfaces which we know how to produce, because that was the weak spot in Eastman’s work, that he just tried some things, but he wasn’t really interested in the surfaces. He was interested in the effect. We wanted to apply it under conditions where this would work, and so I prepared a proposal. And actually my postdoc at that time, my first postdoc was Alex Bradshaw.

HOLLOWAY:  Is that right?

MENZEL:  That name is certainly known.

HOLLOWAY:  Very well.

MENZEL:  And we did this together, and there is a paper by Alex and me describing this machine. The machine, we constructed it, Vacuum Generators built it, and then we started this line of research. Then we worked ourselves into photoelectron spectroscopy. XPS of these well-defined surfaces was very helpful. We did reactions with it, and also we did the physics, many-body excitations and all these things. And there comes the next important co-worker I had, John Fuggle . He unfortunately died very early. At that time he was in England, and I was looking for a postdoc because Alex had not come with me to physics. (He later went to the Fritz in Berlin, actually, and Ertl too). And I was looking for someone, and interviewed Fuggle, and I had the impression this is a guy for us. Then he came, and he worked four years with me, and we did a lot of very interesting things with photoelectron spectroscopy, both UPS, XPS, and x-ray induced Auger. Then the synchrotron business started. I was very involved in the building up of BESSY , the synchrotron  source in Berlin. It was the second source in Germany, actually. The first was and still is in Hamburg (DESY). But we went to Berlin for beam time, and I have been very strongly connected with synchrotron radiation research since then. So we branched out. The desorption still was interesting, and I came back to it now recently in connection with the small particles. But we had many other things that interested us. Desorption, thermal desorption, sticking which is connected to these accommodation coefficients I mentioned in the beginning. And simple reactions, co-adsorption interactions. That really branched out and became very exciting.

HOLLOWAY:  Now another set of characters in this timeframe was Madey and Yates. Could you tell me about your relation with them?

MENZEL:  Well yeah. Good that you reminded me. Ted Madey, who I very fondly remember, he was one of my best friends. I told my wife whenever something happens to me and you need advice, go to Ted. I first met Ted in ’63 when he was a graduate student in Notre Dame and I was a postdoc in Chicago. There was a meeting, was it APS? I’m not quite sure what kind of meeting it was. And there was a small group of people collecting together because they all did field emission, and there were not many of them. And he was there, I was there. We got acquainted , and we later became very good friends. He came to stay in Munich when I then had my institute. He was in Munich twice; once for more than a year, and then again for a shorter period, in the ’70s. I don’t remember the exact dates, but it was in the early to mid ’70s, ’74 to ’75 or something like that. He was at the NBS at that time.  And that is important—that’s funny [laughs]. He brought a ruthenium crystal with him. He somehow had managed to get one—This was difficult at that time. You couldn’t simply go and buy one. You had to convince somebody to make a single crystal, just to produce a single crystal that wasn’t there. So he got one. And we had agreed on this before he came. We had discussed what should we do, and we had agreed if we want to do something that is connected essentially to the basis of catalysis, then we should use a material, not just tungsten, certainly not, and also not just nickel like everybody else then, but something which should be an active catalyst. And we argued, okay, a catalyst must have it easy to change its valency because it has to be oxidized and reduced and give up electrons, take up electrons to induce reactions, and so easily we can jump from one state to another.

And then we found out ruthenium is the material that has the largest number of oxidation states. You can go to every oxidation state between -2 and +8. And so we said this should be excellent. So we said okay, we have to get a single crystal. So he got one through his connections and he came with a single crystal. And so we started on ruthenium. But now I think maybe 200 of my papers are on ruthenium [laughs]. There are guys who will say, “It should be called Menzelium by now!” [Laughter]

HOLLOWAY:  Did you work any with John Yates?

MENZEL:  We did not work together. We were of course acquainted, and the fact that Ted was in so close coupling, really, he made me know him well. But mostly when he went to Europe he went to England. He worked with Dave King. Dave King is another one of these guys. I mean of the heroic times. He still is a very good friend of mine. I should add: Ted Madey, after having been in Munich, somewhat later we exchanged sons. So Tim Madey stayed with us for half a year, and my oldest, Johannes, was with the Madeys for three months or something like that. And in fact Tim still visits us because he had such a good time.

HOLLOWAY:  Did he work technically at the same time? Or it was a cultural interaction? Did he do technical work in the laboratory at the university?

MENZEL:  Tim, no, no. They, Tim and Johannes, were about 12 years old then. They were young then, they were boys. But they just had a real good time because being for a longer time in another country was very, very helpful.

HOLLOWAY:  Adopt a culture and understand it much better.

MENZEL:  Oh absolutely. When Tim went back, he took along two loaves of bread like this because he had come to love it so much!  [Laughter]

HOLLOWAY:  I don’t blame him. The Germany bread is really wonderful.

MENZEL:  Yeah, and we have a special kind in Munich you have to try that’s very good. Well yeah, no, Ted was very close. In fact, after my retirement in 2004 I was there in Rutgers for a while, and we did some things together there, some publications that came out, and it was especially sad for us too that he died so quickly.

HOLLOWAY:  He was well-loved by the society. We have the Ted Madey Award.

MENZEL:  Yeah, yeah, well, it was very nice that Gaede-Langmuir award came and that it—I mean I see it also as an expression of the fact that being old is not necessarily being useless, because I was very impressed by some of the things that have come out in the course of this proposal for my award, which I hadn’t known. Eight months ago I had not known what an H factor is, much less what mine is. And I couldn't have cared less about citation numbers and impact factors. But I must say I myself was impressed by the fact that the both the publications and citations per year over the years have essentially stayed constant after my retirement, and that I like.

HOLLOWAY:  That means that you still have an impact—a very strong impact.

MENZEL:  Yeah, that’s nice. That’s wonderful.

HOLLOWAY:  So tell me about your connection with other people in the United States. Bob Madix you mentioned, for example.

MENZEL:  Bob Madix, yes, there was this trio of crazy young guys in surface science for a while: Dave King, Bob Madix, and me.

HOLLOWAY:  You weren’t crazy, of course. [Laughs]

MENZEL:  Well, crazy—maybe it’s the wrong word, I don't know.


MENZEL:  Wild, yes, yes. I remember times. There were others that were very distinct. For instance, Charlie Duke. I remember it must have been in the early ’70s, one meeting when Charlie was chairing a session, and it must have been an AVS meeting, actually. There were questions in the end, and we knew that Charlie and Dave King had been fighting for quite a while.

HOLLOWAY:  Charlie liked to fight with many people.

MENZEL:  Oh yes, of course, I know that, and I know some stories, too. But this occasion was nice. Dave sat in the back, and raised his hand to pose a question, and Charlie saw him. Dave had long hair at that time. Charlie said, “Yes, ma'am?”  [Laughter]  So these were nice times, yes. And then the other story with the little train. That was fun. [Historical correction added in proof: Actually Bob Madix corrected my memory and told me that it was Bob Merrill who drove the train, not he.]

            Well yeah, Bob is a very good friend. When he got the Somorjai Award two years ago from the ACS, I was there. There I had on an evening jacket with black tie and a shirt like this (indicates creased shirt front), and so I was very happy this wasn’t so serious here.

HOLLOWAY:  We at one time had a tradition where everybody dressed up for the annual dinner, the banquet, but there is no banquet. We had big discussions over many years as to whether or not we should maintain this protocol that had been handed down to us, or open it up and allow everybody to participate. And we decided everybody should participate, and that’s why we don’t have the formality any longer.

MENZEL:  Yeah, I think it’s better that way. I mean there is some effort to not just come in blue jeans; I think that is fine. But having the rules in a way that some people feel excluded, that is not good. That is absolutely correct.

HOLLOWAY:  Now in this process you started off with your education in chemistry and switched into physics.  [Yes.]  But Bob Madix is still back on the chemistry end of it.

MENZEL:  Well yeah, but we do have somewhat different interests. He comes from chemical engineering, and he is really interested in the different processes. He compares different reactions, while I’m much more interested in the basic things happening. And I use certain systems only to vary certain parameters and see how they connect. So this is a different approach, there is no question about that, and you can see it, too. Ted Madey and John Yates, they also had these two approaches, Ted the more physical one and John the somewhat more chemical one, the more system-oriented and not the more effect-oriented. But that doesn’t hinder cooperation. In fact, it’s very helpful if you can put that together.

HOLLOWAY:  Right, complement each other.  [Yes.]  What about the interaction with Gabor Somorjai and Dave Shirley and some of the California synchrotron crowd?

MENZEL:  Yes. Let me start with Gabor who, of course, is oustanding. We’ve known each other for a long time. He certainly is extreme in this chemical approach. And he would call ours “brotlose Kunst”  in German —art which does not give you bread.  [Laughs]  I think he accepts that we do sensible work, but he has a totally different approach. So I’ve never directly cooperated with him, although I’ve cooperated with people in his group: Miguel Salmeron, Michel Van Hove (who helped one of my students, Georg Held – now a professor in England - to start our LEED-IV work), and these people that were much closer, and we have cooperated. In fact I have been on sabbatical in his department, but we have not really had a strong overlapping interest.

Dave Shirley, that was interesting. This was something like…let me see, it must have been also ’76, ’77, really after the first two or three years of our photoelectron work, we really had done a lot of quite basic things in XPS of adsorbates and in x-ray-induced Auger spectroscopy, and I visited Berkeley. Shirley at that time was the overall director in what then was Lawrence Berkeley laboratory. But he also had his group, and I gave a talk on XPS of adsorbates, satellites, how they can be used to get information on adsorbates, and Auger, etc. And after that, they told me later he told his people, “You see, that’s the kind of thing I want you to do.”  [Laughs]  So I think we were recognized there. And then later—I mean I have been in Berkeley so many times, both connecting with Gabor’s large group and also with Chuck Fadley. Chuck Fadley is a very good friend, too. In fact he just sent me an email he had wanted to come and celebrate with me here, but then he has some very urgent things to do and couldn't come. So yes, there always was a very good connection.

But my strongest connection with the States over many years went to IBM Almaden. I mean Dick Brundle, Dan Auerbach, Charlie Rettner, and Paul Bagus were there at the time, and I spent a lot of time there. For 15 years I was in Almaden for at least six weeks in the summer at least every second year. So I have been there very, very often, and we had strong ties there. I have papers there. In the early ’80s I have papers with Dick and with Paul Bagus, and later I worked more with Dan Auerbach and we were well-connected there, yes. And I sent many of my students there. One thing that I feel is important that I didn’t have time to go into yesterday, I mean I had a fantastic series of excellent students. I mentioned Alex and John, but there were many who also got their PhD in my group who are now professors, like Eberhard Umbach in Karlsruhe,  and Peter Feulner (in Muenchen), Herbert Pfnür (in Hannover), Wilfried Wurth (in Hamburg, for synchrotron radiation), and  Hans-Peter Steinrück and  many others. Peter Jakob , who worked with Yves Chabal for a while, and Uli Höfer in Marburg, and Wolf Widdra (in Halle), and Silvano lizzit in Trieste. So there are many, many people who were of course really responsible for what my institute achieved, so they should really have had the award. 

HOLLOWAY:  We all rest on the shoulders of our students.

MENZEL:  Yes, yes, yes.

HOLLOWAY:  You used the synchrotron in Europe a lot, DESY , etc.

MENZEL:  And the ALS. I was at the ALS quite often.

HOLLOWAY:  Have you run some samples on the SLAC, for example?

MENZEL:  Yes. In fact in the late ’70s I was in Stanford several times. That was connected with IBM. I worked together with Joe Stoehr . And at that time I was more interested in doing the desorption things with synchrotron radiation, because at that time that didn’t work yet in Berlin. And in Hamburg, where it would have been possible, I didn’t get beam time, simply didn’t get beam time. So I went to Stanford. So I was in Stanford. There are a few papers from that time with Joe Stoehr. I had one excellent student, Rolf Jaeger , who as a postdoc worked with Joe and stayed in the Bay area. I think he just recently retired from Hewlett Packard .

HOLLOWAY:  Did you interact any with Bill Spicer or Stig Hagstrum?

MENZEL:  We knew each other, I gave talks there, but we never collaborated.

HOLLOWAY:  Let’s go back to talking about your interactions and your later more recent activities in Europe. What have you been up to lately?

MENZEL:  Well, I mentioned this effect that hits in Germany that up to now—It’s just changing, but certainly when I retired, there is compulsory retirement, to start with. I extended it as much as I could, so I left at 68 even though I could have retired with the same retirement pay at 65. So I extended that. But then I had to leave. There is no way you can stay, and I couldn't have grants. Only indirectly- I could have some colleague who acts as my front man, and I don’t like to do that. I want to be responsible. So this is difficult, if you want to keep on working. In fact after my retirement I discussed with several US universities whether they would maybe have a nice job for me, and they all said, “Yes, of course, we would be very happy to have you. But you have to get and bring your own money.” Even then, and now it’s even more difficult, this is difficult if you are not known in the system. So I thought this is not really responsible at my age.  Of course anyone can fall dead all of a sudden, but the older you get, the more likely that is!  [Laughs]  And so for instance if you take on PhD students, and you cannot be sure whether you really can carry them through—I am doubtful. I mean I don’t like that. I think this is not exactly a fine thing. So what I was looking for was opportunities where people would not just be so nice to welcome me to join something, but where it looked like this would really be a non-zero-sum game—each side would have something out of the bargain, and they really would win, too.

            So one possibility was the fact that I am a so-called external scientific member in the Fritz Haber Institute. It doesn’t contain any funds, but it is a basis for cooperation. And Hajo Freund (one of the directors there) is a good friend of mine, and he said, “Okay, why don’t you come on a part-time basis.” In fact I roughly spend a quarter of my time there. I spend a week per month or two weeks in two months, something like that. And he at that time was particularly helpful. He had a group doing photochemistry and nanoparticles that didn’t go ahead as much as he wanted. And also the Japanese head of the group,, Kazuo Watanabe, wanted to go back to Japan. And so I joined this effort. I was in no leading position, but it was advisory, but I had the feeling they quite soon noticed it’s good if they follow my advice!  [Laughs]  And so we got along very well, and were very productive. There are three PRLs  that have come out of that, and many other papers. It’s sort of unfortunate that this ended because this direction has been given up there. And now I have started to have a similar role, although it has not yet adjusted as well, with this high-resolution photo microscope, they call it SMART, this aberration corrected photo electron and low-energy electron microscope. There is also nice collaboration. And I also have some connection with Martin Wolf’s laser group, and so this works nicely. So this is one thing I do.

            Then the second thing is there are people in Munich and the surroundings who are happy if I collaborate. I cannot have a project of my own, but I can be collaborating. So I am in connection with a group that does this atto-second spectroscopy in the Max Planck Institute for quantum optics, and there is a group under my old collaborator, Peter Feulner in my old institute that sort of supplies the surface science part, and there I have joined.

            And the third thing is that I still do synchrotron radiation work, at ELETTRA in Trieste, Italy. We like to exploit this resonant Auger Raman effect where you can sort of get electron dynamics  in the area of around a femtosecond by doing spectroscopy. And we just had beam time two weeks ago for a week, and I was there. And the nice thing is there is this scientist, Silvano Lizzit, with whom I have collaborated for at least 15 years, and in the old days I would come with my group and we would have our own outfit. And now he makes it possible with the means of the synchrotron radiation source that I can do work there without any money, and so that’s nice.

HOLLOWAY:  That’s awful nice! 

MENZEL:  This is very nice. And again, this is win-win. I mean he gets some ideas and some nice results supplied, and he helps me to do it. He gave a post-deadline talk yesterday about that work. So we are now up to doing something on the bandwagon grapheme .

HOLLOWAY:  Well good. Tell me what advice you would have for young people? Young people, I like to try to get advice from senior people. What’s the characteristic that you look for in a student that convinces you that he/she will be a good student?

MENZEL:  Well, yeah, this is not so easy. I have done that many times, especially with my own co-workers, but also with others. For instance, do you know Markus Raschke?  [No.]  He is doing very nice work. He is in Colorado. He was formally my Ph.D. student, but in reality he worked with a postdoc of mine. He also came and asked me, and others also of my students when they got their PhD they wanted to know should they—They are interested to go on, but they don’t trust themselves sufficiently. And I usually told them—The Ph.D., especially in a group like it was mine that had a very strong cohesion, a very good atmosphere, this is a sort of shelter. This is somewhat dangerous in the sense that when it is not there anymore, then you really have to be on your own, and some people find that difficult. And I have seen people where it simply didn’t work, this just collapsed. So I always tell them, “Well, go do a postdocship, at least two years, in an area which is not too close to what you know to avoid being hired as postdoc because you know something specific that you should bring to the institute that hires you. Try to learn something new, and especially try to find out whether you have the, well, what we could call frustration tolerance that is necessary to have a scientific career. It’s not enough to be bright. It’s not enough to understand a lot. I know a few people who are too good physicists to be successful physicists because they will immediately tell you what will not work. And they will probably be right, but if you try anyway, usually you succeed.

HOLLOWAY:  You learn something.

MENZEL:  Yes, at least you learn something. But very often you also find out that the very good analysis such a guy gave was not the complete story. You could find a way. The one thing I learned from Bob Gomer which really has led me—he was really my main mentor, I would say. I had no real other decisive mentor. I made my way quite on my own. But the one thing I really learned from him was if there is something where you have a concept and you can rationally see through it—see the problems, but also see the opportunities—then you can make it work. This works. And young people have to find out whether they can do that. The combination of perseverance, quality of course, I mean knowledge and also…

HOLLOWAY:  Curiosity.

MENZEL:  Yes. This is a good point. I have the attitude I don’t like the research which is based on very strong guiding principles in the sense of what you should look at. Of course that’s necessary. You have to look at things of importance, be it energy or climate change or whatever. But there also have to be people who work more on a basic principle, and for basic research I think the most important thing is serendipity. You have to do good work, interesting work that satisfies your curiosity, and your drive to play. I admit, always I have fun with research because I like to play. I like to play with concepts, see whether this is correct or that, or maybe they’re both wrong or something like that. So I am driven by curiosity, and I go by serendipity. This is not everybody’s sensible approach. Everybody has to find out. But this approach as well as a more mission-oriented approach will depend not only whether you can do it, of course whether you are creative, whether you can have ideas what to do and how to connect things. But perseverance is important—ability to go through hard times and not give up, and some people simply cannot do that. And that you will find out in a new environment with a new project, and you have to adjust, and after two years they usually know whether they have a chance to push through on that. And of course today it’s getting more difficult. I know that. I have grown up, even though they were the heroic times, they were easier.

HOLLOWAY:  It was easier.

MENZEL:  There was expansion everywhere. There was a larger ease. The fact that I could afford not to look at citation numbers [chuckles], it’s a luxury!

HOLLOWAY:  That’s telling. It is a luxury.

MENZEL:  It’s not possible anymore. I know that.

HOLLOWAY:  We’ve covered a lot of topics. I wondered if there was any that you had thought about that I had not touched on.

MENZEL:  Hmm, no. I think we really covered a lot, yes, yes, yes. Just let me reinforce this. The other aspect is being happy and therefore likely to be successful, I think that is connected. What is fun can be much more easily successful. That also has to do with what I would call the human factor in research. Again, it’s a non-zero-sum game. Cooperation is the name of the game and not competition. This is one thing that I’m worried about sometimes. I mean the competitive aspect seems to be stronger in this country than in many places in Europe, but of course we can follow you!  [Laughs]

HOLLOWAY:  Well you lead us in many areas. But each culture has their own characteristic associated with them. But I understand what you’re saying. Well, let me thank you for the interview. I really have thoroughly enjoyed it. And congratulations again on the Gaede-Langmuir Award. I think you’re the perfect person for that where you crossed the two, as you pointed out, surface science and the vacuum.

MENZEL:  Thank you very much, yes. And let me add a general note. I have mentioned many names of people that were important on my way, friends and colleagues and collaborators. But there is no question that there were many more of importance who just did not pop up in my mind at the appropriate moment. To those I want to sincerely apologize. This is just due to an old man’s jumpiness, not negligence.

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