I GEORGE PIMENTEL Univerdty of Colifornia Berkeley, 94720
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Interview with George Pimentel by David Ridgway DAVID RlDGWAY
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University of California Berkeley, 94720
Ridgway:
Were there associates, that is parents, teachers or others who influenced your choice of a career in science? Pimentel: Parental influence was strong, albeit indirect, since neither of my parents had much education. My father reached only the third grade and my mother was taken out of high school so that she could attend a business school. So their influence did not come through their own educations, but rather through the high value they placed on education. They were very enthusiastic about the academic successes of my brother and me, so we got all kinds of encouragement, despite the absence of the implicit environmental encouragement that is found in a home full of books and reading and people inferested in academic and intellectual t h i n ~ saround. I also Rained encouragement lrom my brother who was only a year and a half older than I, a very bright . .person. He offered inteNectua1 companionship, guidance, and encauragement to me as the younger brother. We were very close. He was excellent in mathematics and I tried to emulate him in that, as in everything else. He contributed very positively to my development. Continuing about my family environment, my lather was in construction work, working as a foreman, working with his hands. That led me lo contemplate going in that same direction, only in a prolessional way-trying to realize my father's ambitions that were out of his reach because he didn't have an education. And so my initial expectation when I got out of high school was that I'd become a civil engineer. Ridgway: Did your science education before entering college have either a direct or indirect bearing on your development through the years? Pimentel: In my precollege education I found the more challenging subjects the more interesting. I naturally gravitated toward these subjects and the leading one was mathematics. When I think of the teachers who might have had a special influence on me, it would be the math teachers. Not because any one took a special interest in me personally, but because I liked their subject. As teachers, they kept me interested and those were my favorite classes. I have one additional small experience that may have stimulated my interest in science. I attended ju-
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nior high school in northern Los Angeles and this put me within bicycling distance of Cai Tech. During this time, I occasional~yrode my bicycle over to Cai Tech at night to hear popularized lectures on science by Robert Miflikan. I found these very exciting. It was analogous in certain ways, I would say, to the experiences young people are having today visiting the Lawrence Hall of Science. Ridgway: Are there other factors identifiable and inlluential in establishing your educational goals? Pimentel: Having lived as a child during the Depression years, I was quite concerned that I find something interesting to me in which there was a reasonable opportunity of finding a job. I learned from the career opportunities talks that there was relatively little demand for either mathematicians or physicists except in teaching. At that time, chemistry was the one discipline in which there were lots of career opportunities. And so, chemistry Came up in my estimation. In my first year at UCLA, I changed my registration from civil engineer to a chemical engineer. I held onto the engineer idea because I still had in mind the professional realization of goals that were denied my father because of education. However, as I got deeper into chemistry, I found that the more fundamental aspects were more challenging, and I became a physical chemist. Ridgway: Did you seek out any particular individual to work with and if so, what influenced you? Pimentel: As an undergraduate, my earliest opportunity outside Of the normal academic classroom work was ondergraduate research conducted with Professor W. R. Crowen in quantitative analysis. He would hire two or three good sophomores each year as laboratory assirtants. Ultimately, some of these would work with him in undergraduate research. Later, I became coupled with the physical chemistry instructor, Professor J. B. Ramsey. Of aN my teachers prior to graduate school,
Professor George C. Pimentel is Professor of Chemistry at the University of California at Berkeley. A member of the National Academy of Sciences and a recipient of the Manufacturing Chemist's Association Distinguished Teaching Award, Dr. Pimentel is active in research in molecular structure and bonding, chemical lasers, hydrogen bondmg, mfrared sprctrosropv, and matrix isolatlun methods He has partw~pstedin the Mars probe proprnm. He alio was the Edmr dtheuriginal (:HEM Sludy texts.
Ramsey had the greatest influence on me. His emphasis always was placed on critical thinking. His whole' approach was " I don't want you merely to hear me and believe me or to parrot back things I have said. What I'm interested in is that you think about the ideas I talk about" There was an even more direct influence on me at the graduate level. When I came back to graduate school here at Berkeley, I had decided that I wanted to work if possible with Professor Kenneth Pitzer. He seemed to me the person who was the most exciting, the one most in the forefront 01 our understanding of bonding and molecular structure. Ridgway: What factors influenced your entering the research in which your contributions are so widely recognized? Pimentet: In my earliest years, just out of graduate school, f became interested in spectroscopic techniques as a means of clarifying molecular structure. This seemed to be an opening and exciting lield in which to work and one that coupled nicely to my desire to understand chemical bonding. It gave me the opportunity to provide raw data relevant to chemical bonding with which to advance the field and to challenge existing theory. In fact, that has constituted the framework in which my whole research program has evolved. Early in this period, I became interested in molecules that were not on the chemical shelf, and consequently, that tell into an area of unknown, both concerning what molecular shuctures one would encounter and concerning the applicability of existing ideas 01 chemical bonding. So I set out to try to find ways to study such molecules-free radicals and oLher transient species-and that led me along with my graduate and post-doctoral students, to develop the matrix isolation technique. This technique has been extremely successful and it's very widely used now. Another contribution evolved lrom the interest just described. To investigate these transient species, we were continualfy seeking new approaches. This caused us to develop, alongside the matrix method, what we call "rapid scan infrared spectroscopy". As we did this, we built up a set 01 experimental conditions that were optimum lor exploring what is now the field of chemical lasers. As we developed the rapid scan spectrometer, more or less by accident and luck, we were ready to do just the right kind of experiment to be the first people to discover chemical lasers. So, the matrix isolation technique, with all 01 the new knowledge it has given us on molecular structure and bonding 01 transient .molecules, plus the chemical laser work, with its implications for chemicat kinetics, are two areas in which I've worked that I think are noteworthy. Would you venture an estimate as to general impact Ridgway: of those discoveries? Pimentel: First, the matrix isolation technique has become widely used for a variety ot types 01 studies extending far beyond what we originally intended. Hence, from the point of view of expanding our lundamental knowledge 01 molecules, this technique has become an important one. Yet I don't think it could possibly have the impact that the chemical laser discovery might have it the chemical laser proves to give high energies andlor efficiencies. Either of these would imply unique applications that address some of the crucial societal needs of our times t refer to the possibility that chemical lasers might figure in the devebpment of laserinduced nuclear fusion. If that were to happen, this work would have extremely broad impact on Man's existence. Ridgway: What was the state of the art in your lield when you began?
Pimentel:
This question carries me back to the origin of the matrix isolation technique. At that time it was plain that spectroscopic techniques offered a rich approach to the understanding of molecular structures and chemical bonding, but these techniques were not applicable to transient species without some ingenuity. In the visible-uv spectral region, the tlash photolysis technique was developed, and 01 course, Norrish and Porter shared the Nobel Prize lor that. We were trying to find analogous techniques that would permit us to do similar work in the infrared spectral regions. We found ourselves on virgin ground. After half a dozen years of effort, when we got the first infrared spectrum of a free radical trapped in a cryogenic matrix sample, it was the first such infrared spectrum. So we were not following other people's work-we were trying to figure out how to do it in the first instance. Now, moving ahead a decade to the discovery of the chemicat laser, the situation at that p o h l was a bit difterenl. It had become ctear to quite a number of people that it would be interesting to try to operate a chemicat laser by making use ot the energy released in an exothermic chemical reaction. 01 course, this would require that the reaction selectively put this energy into certain degrees of freedom, but there was evidence that this does happen. So the idea that there might be chemically pumped lasers was not a unique one to this laboratory. The problem was that nobody was having any luck in discovering one. Our special opportunity came lrom the type of experiment we were doing, pursuing transient species. This approach gave us a reservoir of experience with which to attack the problem. One can liken an exicted molecule-a molecule with excess energy in some degree of freedom-to a transient molecule. So all of our background set us up lor doing that kind of experiment. Ridgway: Did you find it necessary to retrain yourself as you entered new fields? Pimentel. The work in chemical lasers illustrates your point. Obviously, I entered that work with a great deal of experience with chemical reactions and spectroscopic techniques. Where I was quite rusty was in the fields Of Optics and the physics 01 lasers. So it has been necessary lor me to relearn classical optics and to keep up with the development of the new optical aspects of lasers. Unfortunately, I go about this retraining in a haphazard and probably ineffective way. Essentially, I Ieam along with my graduate students. We blunder ahead, doing what seems right in the laboratory, and when things don't work, or when we discover that our knowledge of the physics is insufficient to accomplish our goal, then we struggle together to learn it. I'd like to be able to claim that I am orderly in deciding that I should study a particular area-read a couple of books-take a couple of courses-or whatever, but I can't. The only excuse I have is that I'm very busy and it's difficult to set aside the required blocks Of time for such systematic study. Ridgway: Has funding, etc., represented a problem over the years, especially recent years? Pimentel: For my particular case, I've been relatively little held back by funding. Only very recently have I felt any spectre looking over my shoulder that suggests that next year I might be hard-pressed to support my students and their research. I do feel that a bit now, however. Ridgway: What do you see as the future in your specific areas 01 investigation? Pimentel: Well, there's no question that the chemical laser offers an exciting and opening froneer. Furthermore, there are lots of possibilities if you are interested in applications. The one I see as quite novel is that the chemical laser provides inlormation about intimate asVolume 51. Number 4, April 1974
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I had a very similar experience in edlting the high school CHEM Study book. I wanted to bring into the high school chemistry class modern ideas about what motivates spontaneous change, that is, the Second Law of Thermodynamics. As we developed our ideas, perforce without the protective cloak 01 mathematics, I discovered some limitations in my habitual patterns of understanding. Insofar as teaching tends to limit research activities, it might even be a beneficial limitation. I've often asked myself why the excitement and enthusiasm for research can persist in an academic person the entire three or lour decades of his scientific career. In contrast, there is olten a waning 01 enthusiasm and the interest of industrial scientists, despite the rich research opportunities that are available to them on a lull eight hour a day basis. Why this dillerence? t i might be that the mixing in of teaching activities is a refreshing activity on the one hand and perhaps a reliel, on the other, lrom the rigor of continuous research aciivity. Ridgway: Can you suggest changes in the structure 01 the chemistry department or even the Universily that would provide lor greater productivity while still maintaining better or improving the quality of education? Pimentel: I feel that the recent attempts to find brand new educational structures or brand new teaching techniques haven't come up with anything very spectacular. This is usually attributed to conservatism but my belief is that we have evolved to what we are because it provides the most effective way to educate large groups olpeople. There is one experimental area, self-paced teaching, that I might comment about. In some uses, this eliminates lectures and throws both course content and pace into the student's lap. This may work well for the highly motivated student. Our challenge, however, is at the other end 01 the scale. How do we effectively extend educational opportunity to a student who isn't motivated? But this type of student is least prepared to decide content and pace and then to discipline himself to stick with it. For this reason, I think that self-pacing may be a misguided direction. Ridgway: Are there special responsibilities that scientists should bear towards society other than those normally encountered in the lile of the community? Those responsibilities as a citizen, due respective of this profession? Pimentel: I think that a scientist and an engineer alike have very special responsibilities to the society which stem from the strong influence 01 technological developments on every person's lile. The special responsibility I attribute to the scientist and the engineer is an educational and inlormational role. He must use his background and special knowledge to acquaint the person on the street with the nature of science and the likely impact it may have on his lile. He must place his expertise at the disposal 01 our political representatives who must make political decisions about the uses of technology. I do not think that the scientist or engineer should be given the responsibility lor making these decisions. These decisions influence everyone's life but the scientist or engineer is not answerable to the public in the same way a politician is. The latter is elected and if he doesn't respond to the public's desires, there is a mechanism by which they can express their dissatisfaction. So the politician should make those decisions but he has to make inlormed decisions. HOWcan he become informed? The people who have the special technical knowledge must make it readily available to him. That's a civic responnsibilily that we scientists and engineers must lulfill. Ridgway: Do you have any special suggestions for or have you had special experiences in relation to the several ad-
ministrative or polilical bodies that are uniquely concerned with the environment and its protection? Pimentel: Right now, I'm trying to get a research program started that's dlrected toward monitoring urban air pottution. This had placed me in contact with both federal and state agencies that wish to stimulate research connected with the problems of urban air pollution. My experience thus far suggests that these agencies are not operating as well as they must. At this moment, there is a certain panic in our response to the sudden recognition 01 big environmental and ecological problems. When this panic subsides a bit, our agencies will be more effective. At another level, the government is trying to make up its mind on behall of ihe public how much of our resources should go into solving these problems. So far, if's coming too slowly. Money must be provided in bountiful amounts to solve the big problems that we lace on ihe time scale that we have to work on. We have to be willing to devole the same scale of support that we have in the past directed toward defense expenditures. We know that will bring results. Ridgway: What are the major activities that you lee1 have enriched your life outside of the prolessional sphere? Pimentet: I would say that the most enriching aspect of my tile has been being father to ihree daughters. That is an experience that I have enjoyed aN the way. At a much lower level of significance, I would mention avocations and recreational activities. I've always enjoyed athletics and participated in a variety 01 sports. Most of this involves my graduate students, so it brings me into close personal contact with them outside the laboratory. That makes my enjoyment of teaching all the greater. One other exciting period in my life was during my involvement with NASA planetary exploration. I was fortunate enough to have an experiment, one of our infrared spectrometers, on each 01 the Mariner 6 and 7 Mars missions. I found this participation in the exploration 01 the space lrontier so captivating that I applied for the Scientist-Astronaut program and came very close to being accepted. Ridgway: Do you see areas 01 our science or related ones that are being neglected, perhaps even remote lrom your own specialties? Pimentel: There is one trend in chemisiry about which I feet some uncertainty. There is a tendency in chemistry now to segregate the activities that are called iheoretical from those that are termed experimental. This follows the patterns set by physics over the last three or lour decades. One physicist does theory and another does experiments. That has not been the situation that has existed in chemistry. Particularly here at Berkeley, every experimentalist has been expected to be cognizant 01, actively using, and trying to advance the iheory. Only recently have we succumbed to the vogue that one would hire a scientist who is identified as a theoretician by the negative qualities 01 unwillingness andlor inability to conduct experimental work. I lee! that physics has sullered because of this type 01 classification and that it is undesirable for people just starting in science to think that theory and experimenl are separable. So I am unhappy seeing it come into chemistry. I'd like to minimize the change and try to preserve the image that the best scientist is one who understands and advances theory and also does important experiments that challenge and guide these advances. This type of person maintains perspective about the relationship between theory and experiment. Ridgway: The dividing lines in disciplines are disappearing or at least getting fuzzy. Is this process desirable? If so, how can it be speeded up? Pimentel: There is a continuous evolution in what types of Volume 51. Number 4. April 1974
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problems a given discipline will take under attack. This evolution is not something that needs lo be promoted because the evolution takes place no matter what you do. And if the evolution isn't going to happen naturally, legislation won't help. A beautiful example is the movement 01 some areas of spectroscopy out of physics into chemistry. This caused the growth of a new breed of people in chemistry departments who are called spectroscopists and who, fifty years ago, would have all been in the physics department. When fission was discovered, the physicist was conlronted wiih a mixture 01 elements from all over the Periodic Table and it took a very sophisticated chemical attack to discover what changes were taking place. So insolar as disciplinary boundaries exist and persist, they probably have cause. When they need to disappear, they do. What I want is flexibility, not legislation. Ridgway: Let us assume that you are again the 21-year-old, emerging from a ES or BA or a diploma recipient in the year 1973. What do you think you would plan as a
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future career in our present world situation? Of course my answer is influenced by my experiences. I guess I would again consider most seriously an academic career because it has been such a personally rewarding activity. It has kept my ideas alive and in a continual state 01 re-examination. In addition, it has put me in a context in which I could work with brilliant young people on the exciting problems 01 the time. Thus, I would find both the opportunity for intellectual enrichment for myself and the opportunity to help other young people get started in their own creative activities. One of the main gratifications that comes out of a research investigation is there is an excitement when you are on the verge of understanding a phenomenon that is not easily explainable. That has been one 01 the great rewards in my professional life. The other one is the cumulalive reward that comes as you watch young people mature to become productive, creative scientists and to feel that you had some role in helping stimulate and open up their minds.
Pimentel:
