AVS Historical Persons | Frank Propst - 1993

Frank Propst - 1993

Oral History Interview with Frank Propst

Interviewed By Bill Lange, November 18, 1993
 
LANGE: Good morning. I'm Bill Lange, and I have the pleasure of talking with an old friend of mine, Dr. Frank Propst, professor emeritus of physics at the University of Illinois. It's Thursday morning, November 18, 1993, and we're at the 40th National AVS Symposium here in Orlando, Florida. Frank, you and I could reminisce about our extracurricular activities, after-AVS activities and meetings, and have some good laughs, but I don't think that's what the AVS History Committee wants us to record this morning. No golf scores, etc. So, I'm going to ask you a couple of questions. The first would be, how did you happen to get interested in works of interest to other people in the AVS?

probst.JPGPROPST: I was in graduate school at the University of Illinois, and my first advisor was Robert Novick, who had gotten his degree under Lamb at Columbia.

LANGE: The famous Willis Lamb.

PROPST: Right, the "Lamb shift" Lamb. The detection technique that Lamb used to detect the metastable of helium was the Auger process - the emission of electrons due to ions and excited atoms striking a metal surface. Novick had used that process also in his research as a detector, and was generally interested in it just as a surface measurement technique, so he assigned me the task to study the Auger process. He had brought an apparatus with him from Columbia, an old oil diffusion pumped system that he wanted me to use, and I spent a year and a half building an Auger apparatus in that system. I worked and I worked, but the best pressure I could get out of it was about 10-7 Torr. Finally I went to Novick and said, "Look, I can't do a surface experiment at that kind of pressure and it's the best I can do. What do I do?" And he said, "Well, that's pretty good. That's about an order of magnitude better than we were able to get out of it." So, I then started the process of actually constructing a genuine ultra-high vacuum system. RCA had developed a series of stainless steel flanges, using gold O-rings, for the Princeton Stellerator program, so they constructed a mass spectrometer system for us, using that technology and mercury diffusion pumps. So by necessity, I had to become intimately familiar with ultra-high vacuum technology because I was doing a surface experiment.

LANGE: How did you then get involved with the AVS? What was your first contact there?

PROPST: After Novick left the University of Illinois and returned to Columbia, I had to find a new advisor and a home. Dan Alpert, at that time, was the director of the Coordinated Science Laboratory and was promoting vacuum physics and surface physics, so my thesis research kind of gravitated towards the Coordinated Science Lab. Dan was not my advisor. Hans Frauenfelder and Edgar Luscher, who were my advisors, were also associated with the Coordinated Science Lab. I finished my thesis work and then subsequently took a position in physics and in the Coordinated Science Lab, so Dan Alpert became one of my bosses. Dan, as you know, had been long associated with AVS efforts, and he was my introduction, principally, to the AVS.

LANGE: When did you first begin attending AVS meetings?

PROPST: The first meeting was in Cleveland, which was either 1959 or 1960, I believe. In fact, one of the things I should say is that in my recollection here, anything I say is going to be two or three years off because I don't recall exact years. But I believe it was 1959 or '60. I know it was Cleveland1.

LANGE: Then you really got involved with the AVS in the '60s through the journal.

PROPST: Right.

LANGE: Editorship. Want to comment on that?

PROPST: I believe it was around 1963 or '64, a group from the AVS, which I know included you, had been thinking about forming a journal for the Society, and approached Dan Alpert to be the editor. It's my understanding and impression that Dan responded by saying, "I'm too busy to assume the direct responsibility of the editorship, but I'll happy to be editor if I can assign principal responsibility to someone else," and that someone else was me. In any event, Dan came to me and said that he had been asked to be editor, and said that he would accept if I would agree to do all the day-to-day work. So I said, "Fine," and Dan became editor and I was the associate editor. That was around 1964, I think. Either '64 or '65 was the first issue of JVST2, and I believe that I edited the journal from around '66 or '67 until around '68 or '69.

LANGE: You had some other strong involvement with the Society, I know, through the Surface Science Division. I'd like you to tell us a little bit about the incubation stages there, and don't be too modest.

PROPST: Well, during the approximately '65 to '68 period, it seemed to me that the proliferation of Surface Science meetings was perhaps uncalled for. Just about every month, it appeared that there was another Surface Science meeting. And it seemed to me that it was important that there be a central focus, a principal focus, for the surface science community. In particular, people from smaller institutions and programs with smaller budgets simply couldn't afford to attend this large number of meetings, and I thought it was important that there be one meeting that they could attend and feel like they had interacted with a good cross-section of the field. Then the question became, what would be the home for such a meeting? It appeared to me that the American Vacuum Society was a natural home. I did, in fact, look at other organizations, but the AVS seemed to be the most natural one. It had the AIP affiliation and a journal in need of a larger audience. 

I began to campaign in the surface science community for forming a Surface Science Division of the AVS, but it was not extremely well received. There was also a little bit of resistance from the AVS old guard. They were somewhat fearful that too much emphasis on fundamental science might distort the initial intent of the Society. On the other side of the fence, quite naturally, quite a number of the surface science folks were somewhat suspicious of becoming involved with this heavily engineering-focused organization. The resistance on the part of the AVS old guard was very modest. Actually, I would strongly compliment those folks because, not only did they not interfere, but rather shortly they became supportive of the formation of the Surface Science Division. The resistance at that point became primarily from the surface science community. But over a period of time, with a fair amount of campaigning and the effort to hold the first Surface Science Symposium at the AVS, which was at Pittsburgh3 in '68 or '69, something like that, we were able to put together a successful program, and later a Division.

I have always given Charlie Duke a tremendous amount of credit for the successful initiation of the Surface Science Division because I induced him to give an invited paper, and I was able to get a number of other well-respected and well-known people to give invited papers. 

There was, in fact, even some talk of boycotting the Symposium. Paul Redhead told me that some folks at Bell Labs, in particular, were actually going to boycott it. So Paul suggested to me that it might be politic for me to step aside and not be either on the steering committee or be the first Chairman because I maybe had stepped on too many toes in pushing for the AVS. I responded "Great, we'll make Pete Hobson the Chairman", and we did that. I think that took a little bit of the resentment away. 

The first symposium was very successful. I don't know what the attendance was, but from the very start, the Surface Science Symposium drew well. About that time, I changed fields, so I haven't followed the development of the Division, but it has been my observation externally that it has been a very, very good marriage, and it has worked well for both the community and the AVS.

LANGE: Surely has. Let's turn toward your technical work. You might, again, modestly tell us what you consider your more significant technical contributions in the surface area.

PROPST: I don't know whether I would consider them significant.

LANGE: Well, are you proud of them?

PROPST: Yes. When I did my thesis, which I indicated earlier was a study of the Auger process, one of the things that I (and others before then), observed is that, when you bring say a helium ion up to a metal surface when the surface is clean - a tungsten surface in particular - the yield of ejected electrons is considerably higher than if you bring that same ion to a surface that's covered by a layer of gas- nitrogen, hydrogen or oxygen, for example. The question then is, "why does a monolayer of absorbed gas have such a large impact on the Auger yield?" The explanations which had been proposed at the time had been more in terms of the change in the electronic structure of the surface caused by the adsorbed gas. But, to me, these didn't seem to make sense. The interaction involved in the Auger process is a relatively long-range interaction. In addition to that, it appeared to me that the electronic structure of the metal surface was probably not that heavily impacted by a layer of absorbed atoms. So, I tried to think of what other phenomenon might explain that large change in Auger yield. I thought perhaps it's related to the mechanical vibrations of the adsorbed gas. In particular, hydrogen has a relatively large excitation energy in the molecule. So I thought that what might be happening is that, when the Auger electrons attempt to escape from the surface covered with a gas, they stimulate these vibrations, lose energy, and suffer a decrease in yield because the escape probability decreases.

I put together a little trivial model, making a guess of the vibrational frequency and just assuming that the probably of excitation is independent of the n number of the vibration state, and did a very simple, little, straightforward calculation. And lo and behold, it gave not only a rather accurate picture of the change in the yield, but also rather well showed the change in the energy distribution of the electrons which escaped. So I thought it was a pretty good indication that the notion of these surface vibrations might be correct. 

After I got my degree and started doing my own research, I, for a couple of years, kept looking around for a technique to try to directly observe the vibrational states of gases absorbed on surfaces through external electronic scattering. I ran across a paper, and I cannot recall the gentleman's name, he was at Yale, and had studied Raman scattering in gases. He had done a very nice job in making a high-resolution electron spectrometer for this work.

LANGE: A guy named George Schulz?

PROPST: Yes! I remember talking with him and he subsequently invited me to give a colloquium at Yale. He was wonderfully generous and one of the finest people I have ever known.

LANGE: Yeah, that's George.

PROPST: Okay. Just a gentleman of the first order. In any event, I felt that by modifying his apparatus a little bit, ( he didn't have quite the resolution that I thought I needed) I might be able to observe the surface vibrations. The problem is separating the weak vibrational states from that huge elastic peak. At that time, it was a major problem. Anyway, by modifying his apparatus, I thought I could get the resolution I needed. Tom Piper was my student who built the apparatus, and indeed we were indeed able to see the vibrational states of the gases adsorbed on a tungsten surface. One of my pleasures was that one of the first thing that we observed was a 250, 258 vibrational state when carbon monoxide was absorbed on the (100) surface of tungsten.

LANGE: Millivolt?

PROPST: Milli electron volt vibrational state. At that time, there was a fair amount of controversy, but generally speaking, I think the consensus was that carbon monoxide disassociated upon adsorption on tungsten. Our observation was obviously a very clear indication to the contrary, since the excitation energy we observed is quite close to the carbon-oxygen stressing vibration in gaseous carbon monoxide, and that indeed CO was absorbed in an essentially molecular state on the surface. 

So this gave an indication of the potential power of the technique. The technique is called EELS at this point - electron energy loss spectroscopy -- and I believe that an annual international conference is devoted to this technique. So I'm kind of proud of our work. It turns out to be a very difficult technique. I think our first paper was published in something like around '65, '66, in that area, and I believe it took something like six, seven, eight years before the next paper using that technique was published, which is kind of a long time. I believe that all of the results we reported were subsequently confirmed with quite high accuracy.

LANGE: Showing the difficulty of...

PROPST: It's a difficult technique. Huge improvements have been made since then, but that next step really took quite a long time, so I'm a little bit proud of that.

LANGE: The old problem of resolution versus sensitivity.

PROPST: Right. You get all the resolution you want at the price of sensitivity, and you get all the sensitivity you want at the price of resolution.

LANGE: Makes mass spectrometers and all that.

PROPST: Right.

LANGE: I know you have a cute little story about the publication of the work in refereed, peer-reviewed journals having to do with your dissertation work. Would you like to tell us that?

PROPST: In fact, having edited JVST for I guess about four or five years4, I have a lot of stories related to the intrinsic touchiness of the review process, but I think that the incident that happened when I was publishing a paper from my thesis kind of reveals a little bit of it. I sent a paper to Physical Review. It came back with a number of suggested changes. I made what I thought were the suggested changes, resubmitted it, and it came back again. That happened two or three cycles, I guess. So finally, it was clear to me that I was not communicating with the reviewer, and I called the editor to ask if I could directly communicate with the reviewer so I could understand what needed to be done. He was gracious enough to check with the reviewer and got permission. So I called the gentleman that was reviewing it, and I said, "I don't understand what it is that you're asking for. I thought I had responded." His comment was something to the effect, "Well, to be quite honest, I don't understand it. I asked Conyers Herring to look at it, and Conyers says he just doesn't think it's right." The issue was a pretty innocuous little comment about the nature of the Auger process, anyway, So I immediately ran upstairs and asked John Braden to look at it. I said, "What do you think about this?" John looked at it and he said, "Well, that's kind of the way I think about it." So, I called the editor and I said, "John Bardeen says he thinks it looks okay." The paper was published immediately! [Laughter] So, I had a little bigger horse than the reviewer had!

LANGE: That's cute. That's an oddity in peer review.

PROPST: Well, yes. Peer review is a tricky process. We all know some of the difficulties with it. We all also recognize the importance that it plays.

LANGE: Right. Well, I don't really have anything else specific to ask you. Do you have anything else you'd like to add? Any words of wisdom?

PROPST: Yes, I do. I don't know whether it's wisdom or not, but it's an observation. As you know, I changed fields around 1969 or so, and haven't had much contact with the AVS for the past several years.

LANGE: '69 from '93! [Laughter] 

PROPST: But I will say that, as we all know, any organization is no better or worse than the people who make it up. I feel very privileged to have been associated with the AVS and some of the finest people that I've ever known. The list is very long, but I would like to - The highest compliment that I personally can pay to someone is that I consider him to be a gentleman. In this regard, I would like to mention four names: Luther Preuss, Jim Lafferty, Charlie Duke, and Bill Lange. And I want to take this opportunity to say what a lot of people in the Society would say, given the opportunity, and that is, over the years, I doubt that there are any people who have contributed more to the sustenance and growth of the AVS than Bill Lange has. And I would like to say it's been a hell of a lot of fun, and a privilege to hopefully be a friend.

LANGE: Thanks very much, Frank. And I'd like to thank you on behalf of the American Vacuum Society Historical Committee.

PROPST: It's been a terrific pleasure.

LANGE: Thank you.

Notes
1. The 1960 Symposium was held in Cleveland
2. The first issue of the Journal of Vacuum Science and Technology (JVST) was published in 1964
3. The 1968 Symposium was held in Pittsburgh.
4. He was officially listed as Editor from 1967 to 1969

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