Peter, an extraordinarily accomplished, world-famous physicist took a humorous approach to university/academic affairs. He left Michigan at a time when we were looking for a vice president for research, and it may be that his well-known love of a good joke may have kept our administration from making the offer.
Posted by jenszorn on September 28, 2014
https://michiganphysics.com/2014/09/28/peter-franken-on-not-taking-yourself-too-seriously/
To honor the enormous contributions of Dick Crane and Peter Franken to our department, we have installed bronze portrait busts of them in the 4th floor conference rooms (4246 and OPIL) of New Randall Lab. The sculptor is Liz Zorn, the sister of Jens.
–Among his many accomplishments, Crane was recognized for the first (1938) quantitative measurement of neutrino momentum, for accelerator development, for his theory that explained the spiral structure of DNA, for the first measurements of the magnetic moment of the free electron, and for his leadership of the American Association of Physics Teachers.
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–Peter Franken was a guiding spirit over the years 1956-1972 for Michigan’s large and active group in atomic and molecular physics; among his many accomplishments at Michigan, we particularly recall his his work in level-crossing spectroscopy, his leading the team that opened the field of non-linear optics, and his irrepressible joie de physique that inspired dozens of students and faculty.
Posted by jenszorn on September 2, 2014
https://michiganphysics.com/2014/09/02/honoring-dick-crane-and-peter-franken/
LEVEL CROSSING in RETROSPECT
Robert R. Lewis, Professor of Physics Emeritus, University of Michigan
Comments and recollections (2005) on the genesis of the paper “Novel Method of Spectroscopy”
by F D Colegrove, P A Franken, R R Lewis and R H Sands, Phys. Rev. Letters 3, 420 (1959)
Introduction
I have had genuine reluctance to talk about things which happened here 35 years ago, because of a belief in Satchmo Page’s approach to growing old “NEVER LOOK BACK – YOU DON’T WANT TO KNOW WHAT’S BEHIND YOU!”. In fact, it has been fun to meet old friends and to remember the way things were. I’d like to thank Jens Zorn for prodding me into looking back at the work on level crossing spectroscopy. The recollections are necessarily very personal. But all four of the authors are here; in a few moments, the others will get their chance to correct my faulty memory.
Before the Level Crossing
The work was done in the summer and fall of 1959, just one year after my return to UM, and I was just getting settled into a new job and new house. We were expecting our fourth child, so our lives were very full. I was not a regular member of the resonance group, but I often joined the Saturday lunches at the Brown Jug, the nickel bets and the arguments about Resnick & Halliday problems. Physics was exciting then, or perhaps we were all more excitable.
To explain my particular point of view, I have to start the story one year before the experiment had begun. I had come to AA via a summer job at Oak Ridge National Laboratory, as guest of M E (Morrie) Rose, a theorist at Oak Ridge and a UM graduate. We had a common interest in the angular correlation of nuclear radiation and had spent the summer in a fruitless search for “accidental degeneracies” between nuclear gamma rays. The entire theory of angular correlation rested on the interference of different paths in a decay scheme: with transitions A => B => C via a group of intermediate states B, usually the 2J + 1 states with “normal degeneracy” [Figure 1]. It was well understood that when the sub-states B were separated by more than their natural width, the angular correlation would change, leading to “perturbed angular correlations”. The theory of all this was thoroughly worked out in the literature, in part by Morrie Rose, and there were many experiments to illustrate it. This was the main “industry” for doing nuclear spectroscopy, determining spins and parities of nuclear level schemes.
In the summer of 1958, I had suggested to Morrie the possibility that in some nucleus there might be two ”different” groups of states B, B’ which nearly coincided, an “accidental degeneracy”. There should then be an anomaly in the angular distribution of the gamma radiation, due to interference of the paths ABC and AB’C [Figure 2]. We invested quite a lot of time looking through the nuclear data tables and talking to experimenters, without finding a good case. It was the proverbial “search for a needle in a haystack”: nuclear levels have gamma widths Γ ~ 10-2 eV and separations ΔE ~ 10+5 eV, so we had a chance of success about 1 in 10 million! We never considered looking at atomic transitions, where the level spacings are much closer. And we never dreamed of moving the levels into degeneracy; we were thinking about nuclear physics where such things were not possible!
Near the Level Crossing
I first learned of the helium experiment about one year later . It had been underway for some time, and was originally planned as a search for the electron spin resonance in triplet helium. This required a strong magnetic field applied to a sample of metastable helium atoms. When the magnetic field was turned on, two strong resonances were seen unexpectedly at low magnetic fields, about 600 Gauss. From the beginning, it was understood that these resonances were at the location of the crossing of 3P levels; the results for the fine structure separation were presented at the optical pumping conference that summer (1959). The question was not “where” these resonances occur but “why”. Peter Franken went from door to door down the first floor of Randall (theory row), trying to interest people in this problem.
I was slow to respond because I didn’t really understand what they were doing. I had never worked in atomic physics and only knew what we had all learned from studying quantum mechanics. I was teaching the graduate courses in quantum mechanics and was immersed in the quantum description of everything. After several visits from Peter (he was very persistent!), I agreed to visit the lab one Saturday and look over the apparatus [Figure 3], a standard Varian magnet with a helium discharge lamp and a helium sample between the pole tips. I watched the scope as they tuned the magnet, giving a nice Lorentzian in the transmitted light, [Figure 4]. But I still didn’t understand what they were doing, and why the resonance was a problem.
What motivated me to continue was to explain it all in quantum language: I was struck by how much they used classical physics instead of quantum physics in their discussions. I’m sure I was a bit arrogant about this; it seems to me now that the essential (missing) point could have been understood either in quantum or classical terms. Nonetheless, I thought I understood the origin of a “Lorentzian resonance” in a quantum system, in terms of the effect of an oscillatory perturbation , a la Schiff. If the frequency ω were tuned to the energy difference (E1 – E2), the transition probability would go through a maximum [Figure 5]. Note that the abscissa in Figure 5 is frequency, whereas Figure 4 was drawn versus magnetic field; that detail had not penetrated my thinking. Actually, Schiff’s approach was appropriate for the ESR signal and most other resonances observed by the “resonance group”, and therein lay the puzzle. It simply didn’t predict anything special when two levels crossed!
Fortunately, after 35 years one forgets all the blundering and confusion, but I remember with startling clarity the time and place at which things suddenly “clicked”· It was a hot Saturday in July; we were getting ready for a cocktail party in our basement to avoid the heat and I was driving east along stadium Blvd, heading for the Party Store to get the drinks. As I approached the light at Main Street, it suddenly hit me: they were not tuning the perturbation a la Schiff, they were changing the magnetic field to produce an “accidental degeneracy”. Then things began to fall into place for me, the light not being emitted or absorbed but was scattering via two paths which were interfering when two levels overlapped. This was the optical analogue of the effect Rose and I had searched for in nuclear gamma rays, except that one photon was being absorbed and the other emitted, instead of two successive emissions [Figure 6). The intermediate energy levels versus magnetic field were being probed [Figure 7].
It was then a simple exercise in quantum mechanics to calculate the amplitudes of the various paths, adding them coherently at resonance and adding them in quadrature when they were far apart. It had all been reduced to algebraic tables of the dipole moments from Condon & Shortley. predict which level crossings would interfere, and how the results would depend on the light polarization.
My next most precious memory is another Saturday, probably just one week later; as I recall it, everything interesting happened on a Saturdays. I think I was busy with classes and other things all week long and was a “resonance physicist” on the weekends. There was a sacred tradition of contesting important ideas with “nickel bets”; the real money was involved, but the stakes were much higher than the coins we used. I remember winning three nickels from Peter IN ONE SATURDAY. Unfortunately, I can only remember what two of the bets were about; the third nickel has fallen through the cracks in my memory.
The first bet was about the dependence on the polarization: the “back of the envelope” algebra indicated a strong dependence on polarization but the polarization didn’t seem to affect the experimental signal. Peter became suspicious of the Polaroid they were using, so he cut two new pieces and rotated one in front of the other in the 1 µ light from the helium lamp; again nothing happened. What had been sold as a polarizing material simply didn’t polarize at 1 µ! Remember that the line was not visible, so one couldn’t SEE any of this. With a better polarizer, the dependence on polarization was observed and a nickel changed hands.
Another bet concerned the behavior in the forward direction: the detector was mounted straight ahead of the sample, but our algebra said the total cross section should not show a signal. We eventually agreed that the observed signal was due to the forward scattering of light, which should show a signal, not to the attenuation of the incident beam, which should not. So nickels changed hands, we became proficient in doing the algebra and we gained confidence that we had understood the essential features of the signal. It was due to the interference of paths when the levels were in “accidental degeneracy”. The PRL article was written and quickly submitted.
It was also recognized that this is the high field analogue of the “Hanle effect”, seen in the 1930’s near zero magnetic field, when the “normal degeneracy” was removed by the Zeeman effect. This effect had in fact been interpreted classically. Peter arranged a visit to AA by Hanle a few years later, and there is a nice photo of us (minus Don Colegrove) taken by Jens Zorn at the Resonance Colloquium.
After the Level Crossing
What happened after the submission of the paper reveals a lot about our motivation. Don Colegrove went on to finish his thesis in optical pumping; he mostly wanted to get his degree and a job. Dick Sands went on to further work in electron spin resonance; he really wanted to do biophysics.
I was fascinated not with the atomic physics, but with the quantum mechanics. I worked out (but did not publish) the line shape at a level crossing of higher order, where the levels “kiss” instead of ”cross”. It was an interesting mathematical possibility of no earthly importance, and it was never published. I also presented a paper on level crossing at a local meeting of the AAPT in Flint. It proposed using level crossing as a demonstration of the principles of the famous “two slit interference” discussed in every book on quantum mechanics. My talk there was a bomb because everyone else was more interested in Ohm’s Law than in the principles of Quantum Mechanics. Thirty five years later, I still feel that it is a beautiful visualization of the interference of paths, and I have waited patiently for someone to make a visible demonstration using diode lasers and sunglasses. I did not consider writing a longer paper on the angular distribution including level crossings, because I felt that the theory of angular correlations of nuclear radiations could easily be adapted for that purpose.
Peter went on sabbatical leave to Oxford and wrote a basic paper analysing the level crossing as a general method in atomic spectroscopy. It is interesting that he discussed it with Morrie Rose, as well as with Willis Lamb and others. He treated level crossing as a general method of spectroscopy, a useful tool for making precision measurements of level widths and energy separations. Peter deserves all the credit he received for spreading the message of ”level crossing spectroscopy”. In the decades since then, level crossing has grown to become a line item (#32.80Bx) in the PACS classification of topics in physics!
Posted by jenszorn on November 18, 2013
https://michiganphysics.com/2013/11/18/level-crossing-spectroscopy/
Peter Franken was a member of the Michigan physics faculty from 1956 until 1973 when he became the founding director of the Optical Sciences Center at the University of Arizona. Prior to 2005, this unit was among the world leaders in optics research; moreover it had a strong teaching component. But it did not have full authority to determine curricula and academic promotions. For administrative reasons the OSC had been under repeated, increasing pressure from the provost to join one of the existing colleges such as the College of Science or College of Engineering, but the Optics people were not enthusiastic about that.
Now quoting from R.L. Shoemaker’s article in “Optics and Photonics News”, October 2005, pp 12-14: “The last time the University asked OSC to join another college, the provost told the Center’s director that OSC could join any existing college that they wished — but he ultimately regretted the wording of his request. Franken, the Center’s director at the time, responded that the OSC would like to join the College of Medicine, with salaries adjusted to be commensurate with those of the well-paid faculty there.” Franken’s response ended the attempts of the provost and, finally in 2004, the OSC became the College of Optical Sciences with the authority and profile of a self-standing academic college within the University of Arizona.
Posted by jenszorn on October 24, 2013
https://michiganphysics.com/2013/10/24/frankens-black-belt-in-administrative-ju-jitsu/
Those few of you who are of a certain age may remember a book and television series of the early 1950s called “I Led Three Lives.” I have known Gabi for a very long time, but I have not known all of his lives. I have learned what I know of his early life in bits, gleaned from conversations over the years. Gabi spent nearly thirteen years of his life in Vilna, then geographically in Poland, now Vilnius, capital of Lithuania.
His father, Max Weinreich was director of the YIVO, an institution devoted to the language, culture and literature of Yiddish, Gabi’s first tongue. The family had a cook with whom Gabi also spoke, in what he later learned was a different language, Polish. He grew up in a richly cultured, secular, socialist Jewish family in a larger Jewish culture, embedded in an urban environment. In September 1939, the Germans invaded Poland from the West and the Russians from the East. Vilna was in the Eastern portion, occupied by the Soviets. Gabi once told me that he had heard on Soviet radio that Stalin was the world’s greatest skier. I recall speculating with him whether he was a theoretical or experimental skier.
In late 1940, Gabi’s father and older brother attended a conference in Sweden, and went from there directly to the United States. Gabi and his mother remained in Vilna, awaiting documents which would permit them to emigrate. As I learned ten years ago, when I was bitten by a dog on the eve of my wedding, Gabi was bitten by a neighbor’s dog while they were awaiting the papers. He was given the Pasteur rabies treatment (The dog actually was rabid.), the papers arrived, and he and his mother departed. Their route took them to Moscow, on the Trans-Siberian railroad to Vladivostok (an eleven day journey), to Yokohama, San Francisco, and then to New York, where the family was re-united in early 1941. Hitler invaded the USSR the following June. The society of Gabi’s childhood was “disappeared.”
Gabi spent his teens in the Washington Heights section of Manhattan (near the George Washington bridge). He started school knowing practically no English (On this point I have only his word; actually I am skeptical.) He took phonetic notes, which his brother (a linguist) helped him decipher. One of his early recollections is hearing a teacher declare, “The United States is a capitalist country.” Startled, Gabi looked around to see if anyone else noticed what she had confessed. He, after all, knew that this was true, but he was amazed to find that anyone would admit such a thing.
He was an undergraduate at City College and at Columbia, which brings me to the point when we first met.
He and I began graduate school at Columbia in the Fall of 1948. I am not certain whether we met that first semester, when I was still supported by the GI Bill, and did not have an office at the Pupin Lab. I became a Teaching Assistant the next term, and Gabi and I arranged to share an office (with Andy Sessler) the following Fall. I remember Gabi walking into the office with a Russian book he had found in a bookstore. (Russian was another language he “did not know.”) The book was Landau and Lifshitz’s Classical Theory of Fields. We were absolutely stupefied by Landau’s elegant (and totally new to us) treatment of Relativity.
In the Fall of 1949 we began our research, he with I. I. Rabi and I with C. H. Townes. Both of us began working with younger physicists, recent doctorates: Gabi with Vernon Hughes, and I with Arthur Schawlow. Our labs were three doors apart on the tenth floor of Pupin. Gabi’s lab, and the atomic beam machine he inherited, had just given the result which first showed the electron to have an anomalous magnetic moment.
Rabi was a formidable figure, and dominated the department in many ways. He was actually chairman only in our first years there, but remained the dominant personality much longer. Henry Foley used to say that at the Faculty Club, the physics people had two types of luncheon conversation. If Rabi was absent, the topic was Rabi. If not, there was some difficulty finding a topic until Rabi chose one. He seemed to find it necessary to dominate and intimidate everyone in the department-students and faculty alike. The first person who could deal with him was Jack Steinberger who, along with Robert Serber, arrived at Columbia in the 1950s as part of the exodus from Berkeley over a loyalty oath. Steinberger (never overburdened by politeness) and Rabi were overheard by a student in a conversation which went like this:
Rabi: I don’t know about that.
Steinberger: Well I do.
(end of conversation)
The late 1940s were past the time Rabi considered the “Golden Age” of his physics. He was, nonetheless, still a very creative thinker. He was also involved, at the time, in fateful decisions in the “corridors of power.” In the Fall of 1949, he was a member of the General Advisory Committee of the Atomic Energy Commission which recommended against a “Crash Program” to develop a Hydrogen Bomb. This recommendation was to play a key role in the loyalty hearings “In the Matter of J. Robert Oppenheimer” in the Spring of 1954. It was reading Rabi’s testimony in that affair that first made me appreciate his strengths.
Experiments, in those days, had a good deal of glass apparatus, and we both learned a certain amount of glass blowing (as did our slightly senior colleague, Peter Franken). When Gabi needed a professional, he called on Karl Schumann, the University glassblower. Karl was a temperamental artist, who spoke a colorful, heavily-accented, English, referring to his colleagues as “neon sign benders.” Gabi’s experiment used 3He (Rabi obtained 3 NTP cc of gas for him.), for which a Gabi bought a commercial glass mercury diffusion pump. It was a glorious object, very large, and full of jets, water jackets, and spirals for the returning mercury. A group of us gathered around when the day came for Schumann to glassblow the pump into the apparatus. Karl preferred to work in front of an audience, and invited one into his shop at the end of each work day. The great man arrived, put down his tools, and walked slowly and silently around the marvelous new pump. Then he turned to Gabi and said, “What did you pay for this piece of crap?”
At Columbia, Gabi first taught a course in Physics of Music. He amazed me, in demonstrating the asymmetric nature of the transient produced by a piano, by playing a piece of classical music backwards, recording it, and playing the tape backwards. The music was then forward, but each note was time-reversed. The notes sounded the way a harmonica does if one inhales rather than blowing.
In 1953 Gabi completed his Ph.D. and went to Bell Labs, where he was interviewed and hired by William Shockley (who had entertained a Columbia colloquium by playing “How Dry I Am” on an audio oscillator made with a germanium transistor and powered by a battery made of a couple of coins and some damp paper).
His Bell Labs physics which I know best is something called the Acoustoelectric Effect which he discovered and named, only to find that someone else had apparently done the same thing earlier. (It is characteristic of Gabi to work something out from the beginning before going to the library.) He was very discouraged, and retreated to his laboratory for a few days, doing some therapeutic glassblowing, before going to the library to read the earlier paper. He found that, in fact, it missed most of the crucial physics, now described by the so-called “Weinreich relation.” In the summer of 1957, Gabi invited me to join him at Bell Labs to test the theory, and see what we might learn from experiment. He and Harry White, his technician, had already verified some of the predictions in a preliminary experiment. Harry learned to grow his own germanium crystals, I succeeded in getting an apparatus through Bell Labs’s shop, we learned how to operate a hydrogen liquefier, and we were taking data by the end of the summer. The result was some pretty physics which led both of us to some other interesting experiments.
Gabi came to Michigan in 1960, I in 1963. He developed a graduate course in Solid State Physics, from which came his 1965 book Solids: Elementary theory for advanced students. He taught Physics 510 (then a course in Classical Thermodynamics, out of which came another book Fundamental Thermodynamics, in 1968. Since he and I had adjoining offices, with a connecting door, I was forced to learn a great deal during this period. His unconventional and original approach in the books has limited their adoption as textbooks in standard courses, but they continue to be cited in the literature by an enthusiastic, if too narrow, audience. He then undertook a complete overhaul of our General Physics courses for science and engineering students. The result, again, was very original but, like the Feynman Lectures, was not widely regarded as suitable for a standard course. He also developed a very successful course in the Physics of Music.
At Michigan, Gabi’s first research was as part of the “Resonance Group”, which Peter Franken and Dick Sands has started earlier. He made a crucial contribution to the production of optical second harmonics by pointing to the necessity of using a material lacking inversion symmetry. His first Ph.D. students worked in areas of Solid State physics which grew out of his work at Bell Labs.
After some work in Atomic Physics, collaborating with Jens Zorn, he started his own work in Musical Acoustics. One of his first efforts was to try to understand why a piano has more than one string for each note. The result, showing why the piano’s transient is not a simple exponential decay, appeared both in the physics literature and in a cover article in Scientific American. One of his major accomplishments was to convince the National Science Foundation to support his work, in a field previously denied support as a matter of policy. He had to do a lot of convincing, at the end of which Senator William Proxmire singled out his grant for a “Golden Fleece” award. Gabi explained the value of his research to the Senator so convincingly that Proxmire was reduced to complaining that he wished the NSF officials had been nearly so persuasive. In his research on the violin, one of his important accomplishments was to show how the outgoing wave from a violin could be measured, even in the presence of incoming radiation. Such a measurement was possible since both the amplitude and phase of a vibration are accessible. Previous workers had generally relied on intensity data only. He also devised ingenious arguments, based on reciprocity, to relate vibration of the violin body to the radiated acoustic field. His recent violin research treated the physics of a bowed string and utilized a computer in a feedback loop, constituting what he calls a “Digital Bow.”
He has maintained a collaboration with acousticians at Pierre Boulez’s institute IRCAM (near the Pomipdou Centre), has supervised doctoral work at French universities, and was awarded the International Medal of the Société francaise d’acoustique in 1992. Within the last few years, he has been the Klopsteg lecturer of the American Association of Physics Teachers, and a Distinguished Public Lecturer (in Boston’s Symphony Hall) of the Acoustical Society of America. After the death of his friend Arthur Benade, Gabi served as the Acoustical Society’s editor for musical acoustics.
In addition to the research he has published in Solid State, Atomic Physics, and Musical Acoustics, he and I have co-authored several papers. Most of this research had the form of my posing a question and Gabi answering it.
It would not be right for me to omit a part of Gabi’s life which has been of great importance to him in recent years. Beginning approximately twenty years ago, he became increasingly interested in religion. His study of scripture required him to read Hebrew, another of the languages he does not know and Greek. He followed a complicated trajectory to ordination as a priest in the Episcopal Church in 1986, to service as an Assistant Rector at a church in Ann Arbor, finally (in phased retirement) to become half-time Rector of St. Stephen’s parish in Hamburg. It is an activity from which he clearly derives a great deal of satisfaction, and through which he accomplishes good in the community.
He and I, of course, discuss religious matters a good deal over coffee. He applies the same startling originality and intelligence to these activities as he does to his physics.
Posted by jenszorn on June 3, 2012
https://michiganphysics.com/2012/06/03/sanders-at-weinreich-retirement/
How did it come about that Peter selected me to perform the original optical harmonics experiment? I was only a sophomore at the University of Michigan, taking a first-level physics course at the University of Michigan. After class, I asked Professor Franken what he would expect to happen if I applied an intense pulsed magnetic field to an aluminum cylinder by magnetic induction. He said…”I suspect it would be crunched short and fat”. My answer was…”No, it is crunched long and skinny”, whereupon I pulled out a cylinder I had so crunched in my home lab as a high school student. Peter then said: “I have a project for you to do this summer!”
He provided me with the first commercial (Trion Instruments) ruby laser, which put out 3 joules in 2 milliseconds (Q-switching had not been achieved yet). Realizing that harmonic production would scale quadratically with power, I intentionally pushed the flash lamps to their explosion point, thus managing to produce an initially invisible spot on a glass spectroscopic plate. I tossed the first plate into the trash, but then realized that a closer examination under the microscope might reveal something. It did. The one piece of evidence for optical harmonics (a visible speck on a spectroscopic plate), sent as a figure with our paper into Physical Review Letters, was removed by the journal’s lay-out person who had assumed it to have been left by a fly.
Here are a few of Peter Franken’s characteristics:
• Peter loved to shock or startle people; he was always full of mischief!
• Peter liked to play the “devil’s advocate” whenever possible. He would question the viability of a new proposal or concept, and could usually debunk them with a mental calculation if they were not sound; and he would often challenge the victim with a nickel bet (payable only in check- to be framed on his wall). He often lost, since he challenged everything – but sometimes he won.
• Peter never took himself too seriously, and he had the nerve to try anything. He was fond of saying: “It is easier to be forgiven than to get permission”, or “I’m going to get kicked in the ass for this, but my ass is big enough to take it.”
• When Peter felt someone had been seriously wronged, he has been known to make it a long-term commitment to defend that person, or to help them in every way possible. Examples: Gordon Gould with his laser patent; Walter Spawr with his trial defense and ongoing vindication.
• Peter had a very broad-based imagination and creativity in physics, but also viewed administrative problem-solving as nearly as interesting. • Peter felt genuine concern and affection for many – an aspect which transcended even his formidable talent for doing physics.
Alan Hill, 2011
Posted by jenszorn on May 24, 2012
https://michiganphysics.com/2012/05/24/franken-remembered-alan-hill-2-2/
MichiganPhysics 