(b. Odessa, Russia, 12 February 1914; d. Penn Valley, Pennsylvania, 25 July 1983),
condensed matter physics, nuclear physics, high-energy physics.
Primakoff made major contributions to the theoretical physics of condesnsed matter and to nuclear and high energy physics. The so-called Primakoff effect deals with a method for determining the short lifespan of the meson from photoproduction. His name is also associated with topics as varied as spin waves in ferromagnetism, and the underwater propagation of shock waves. In addition, Primakoff was an expert on the manifestations of weak interaction phenomena in nuclei, such as double beta decay, muon capture, and neutrino scattering.
Youth Henry Primakoff was born in Odessa in 1914. Through his mother, Primakoff was descended from a large, assimilated Jewish family of merchants who had lived in Odessa for several generations. Through his father, Henry came from a Greek Orthodox family of wealth and prestige, who banished Henry’s paternal grandfather and father from the family estate for marrying Jews.
Primakoff’s father, a doctor, was wounded while serving in the Russian army in World War I and died in 1919. About two years later, Henry’s mother and her parents decided to leave Russia and join an uncle who had settled in New York. This required escaping across the nearest border into Romania, trudging for long night hours through woods, and hiding by day in remote farmhouses. After a long and difficult odyssey, including a long wait in Bremen before obtaining passage to the United States, they finally arrived in New York in 1922. Henry became a U.S. citizen in 1930.
The family settled in the Bronx where Primakoff learned English. He also learned, the hard way, that some four-letter words should be used with discretion. He excelled in high school where he took an active interest in politics and journalism, becoming editor of the school paper one year and class president another. He was offered
scholarships to Harvard and Columbia; he chose to begin his freshman year at the latter, in the fall of 1931.
Education His initial interests at Columbia were writing and philosophy. Primakoff’s focus did not shift to science until he was a junior and to physics only in the middle of that year. He was one of a handful of students who constituted an informal club to study special relativity from Richard Tolman’s Relativity, Thermodynamics and Cosmology (1934). Club members who went on to distinguished careers in physics include Norman Ramsey, Nobel laureate; Herbert Anderson, student and longtime collaborator of Enrico Fermi and codiscoverer of the (3,3) resonance in meson-nucleon scattering; Robert Marshak, coinventor of the universal (V-A) form of weak interactions and founder of the Rochester conferences in high energy physics; and Arthur Kantrowitz, former director of the Avco Everett Research Laboratory. Primakoff spent his senior year at Columbia taking graduate courses; in one laboratory course he met his future wife Mildred Cohn. Pursuing her own career in science, she would become a very distinguished chemist, particularly known for the application of nuclear magnetic resonance to biochemistry.
Primakoff’s graduate studies began at Princeton. In those days there was little financial aid. With help from his family and money either saved from his undergraduate scholarships, or earned from various odd jobs, Primakoff managed to pay Princeton’s tuition (about $100) and support himself for a year. Then he obtained a fellowship at New York University, where he earned his PhD in 1938. He married Mildred Cohn in May of that year.
Overview of Career Despite the Depression, they both found jobs, Cohn in the Biochemistry Department of Cornell Medical School in New York and Primakoff first at Brooklyn Polytechnic Institute and then at Queens College. After Pearl Harbor he began to work on a navy project concerned with sonar and submarines. When asked by J. Robert Oppenheimer, Primakoff declined to join the Manhattan Project on the grounds that he wanted to work on projects for the present war and not the next one. He thought an atomic bomb could not be built in time, and was greatly surprised by the news of Hiroshima.
At the end of World War II, Primakoff took a joint physics and mathematics position at NYU, but a year later Arthur Hughes and Eugene Feenberg persuaded Primakoff to join the physics faculty of Washington University in Saint Louis. Cohn found work in Carl Cori’s department at the medical school, so in 1946 they moved to Saint Louis, Missouri.
In 1959 Primakoff and Cohn, by now equally established scientists, were offered appointments at the University of Pennsylvania. Before that job offers had been to one with the promise of something for the other; then Penn offered appointments to both Primakoff and Cohn. They accepted, Primakoff becoming the first Donner Professor of physics at Penn and Cohn eventually receiving a chair in biochemistry. They were both elected to the National Academy of Sciences, Primakoff in 1968 and Cohn in 1971. Primakoff remained active in teaching and research at Penn until his death from cancer in 1983.
Early Research with Holstein Primakoff’s first published research paper (1937) was on the force between protons and neutrons due to the exchange of neutrino-electron pairs in the then new Fermi theory of beta decay. It was a prophetic choice of topic because after the war Primakoff, as already mentioned, devoted a great deal of attention to weak interactions in nuclei.
While still a graduate student, he began possibly the best known paper that he wrote, certainly the best known in what is now called condensed matter physics. While he and fellow student Theodore Holstein investigated the field dependence of the intrinsic magnetization of a ferro-magnet at low temperatures, they had the ingenious idea of expressing the spin operators that appear in the Heisenberg exchange interaction model in terms of boson creation and annihilation operators. With appropriate approximations, which turned out to be equivalent to approximations used by Felix Bloch and by C. Møller in a very different and less complete treatment of the problem, they were able to diagonalize the Hamiltonian, including magnetic interactions as well as the exchange and dipole-dipole interactions.
Their essential idea was that, though the magnetic moments of most of the atoms in the ferromagnet line up with the external magnetic field, temperature agitation will always cause a few to deviate from complete alignment. Holstein and Primakoff used the boson transformation to demonstrate that the spin deviations were not localized on a particular atom, but propagated through the crystal as spin waves. Spin waves, originally proposed by Bloch, are now regarded as the principal modes of excitation of ferromagnets, and in recent years they have even entered nuclear theory.
Although this paper has become a classic, scientists did not recognize its importance until several years after the end of the war. Its impact began to be felt when in 1945 Oxford physicist James H. E. Griffiths discovered ferromagnetic resonance effects of unusually large frequency compared with the Larmor precession of electron spin in a magnetic field. Charles Kittel, then at MIT, gave a classical interpretation of the anomaly in 1947 and a year later Dirk Polder, of Bristol, derived the Kittel formula using quantum mechanics. Polder’s derivation used the Holstein-Primakoff method for describing the quantum mechanical states of a ferromagnet and the corresponding energy eigenvalues. Subsequently, Kittel and Joaquin Luttinger used an “ingenious but somewhat devious method” (quoted by Rosen, 1995, p. 273) to calculate directly the ferromagnetic resonance frequencies from one term in the appropriate Hamiltonian. Holstein and Primakoff’s paper received its due recognition once the relevance of quantum mechanics to ferromagnetism became firmly established.
Even though the Holstein-Primakoff transformation was a seminal contribution to theories of ferromagnetism and anti-ferromagnetism in the 1950s, and remained famous, it is interesting to note that neither Holstein nor Primakoff ever worked on this subject again.
War Research Although Primakoff did not participate in the Manhattan Project, he did do some research relevant to the Bikini underwater tests of nuclear weapons. There was concern at the time that the test could set off a powerful tidal wave that would cause serious destruction in the Pacific basin. Applying methods Geoffrey I. Taylor had used for shock waves in air, Primakoff found a simple, exact solution for the problem in water at high energy and showed that the properties of a shock wave, including its height, are all determined solely by its energy. Known by some authors as the Primakoff wave, the result was never published in the open literature, but Richard Courant and Kurt O. Friedrichs (1948) describe and attribute it to Primakoff.
With his Washington University colleague Eugene Feenberg Primakoff coauthored a paper on collapsed nuclei; it anticipated ideas developed many years later by Tsung-Dao Lee and Gian Carlo Wick to study super-dense matter. They also wrote on the interaction of cosmic-ray primaries with starlight and sunlight, showing that cosmic ray primaries should consist mainly of protons because energetic electrons would undergo too much scattering from photons in intergalactic space (through the inverse Compton effect) to reach the vicinity of the Earth. Primakoff’s publications on muon decay, muon capture, and hypernuclei also evoked considerable interest. In a seminal paper, in collaboration with Sergio DeBenedetti, C. E. Cowan, and Wilfred R. Konneker, Primakoff derived the basic formulas for the angular distribution of photons from positron annihilation in solids; it is still quoted today. During this period he also first wrote on the so-called Primakoff effect and on double beta decay.
Double Beta Decay Double beta decay takes place extremely slowly, being in a certain sense a succession of two ordinary nuclear beta decays, but it is important for fundamental questions regarding the neutrino. If the neutrino has a mass, and if it is its own antiparticle, then it is possible for double beta decay to take place without the emission of neutrinos in the final state; the neutrino emitted in the first ordinary beta decay is reabsorbed in the second. With the advent of the standard model for particle physics, the study of neutrino properties has become important for the new physics.
In the 1930s Maria Goeppert-Mayer, Ettore Majorana, Giulio Racah, and Wendell Furry had studied double beta decay. In 1959 Primakoff and Peter Rosen published a significant review article that formed a bridge between the earlier work and the important developments brought about by the discovery of parity nonconservation and the two-component neutrino in the late 1950s. For many years it was a standard reference as well as providing a useful starting point for the modern developments in double beta decay of the 1980s.
Primakoff Effect At Penn Primakoff extended his work from 1951 on the photoproduction of the neutral pion in the electric field of the nucleus. The essential point of this paper, which has come to be known as the Primakoff effect, is that, under certain well-defined kinematic conditions, the photoproduction of neutral pions is controlled by exactly the same interaction as the decay of the pion into two photons. As a consequence the lifetime of the meson, which is difficult to measure directly, can be deduced from measurements of photoproduction, an easier task. With C. M. Andersen and Arthur Halprin, he applied this approach to the lifetime of the newly discovered eta meson, a pseudoscalar meson such as the neutral pion, and to the production of vector mesons. The Primakoff effect is now the standard method of measuring neutral meson lifetimes, of use as well for obtaining limits on the existence of conjectured but still undiscovered neutral mesons such as the axion. It also features prominently in astrophysics, providing a means of estimating some non-trivial stellar cooling mechanisms.
Muon Capture At Penn, Primakoff continued to work on weak interactions. With the introduction of the universal V-A interaction for all four-fermion weak interactions in 1958, Primakoff had realized that the rate for muon capture in nuclei (the second leg in the Puppi triangle connecting different weak phenomena) would be sensitive to the hyperfine splitting of the parent atom. Jeremy Bernstein, T. D. Lee, and Chen Ning Yang had independently made the same discovery and they invited Primakoff to be a coauthor. Afterwards he developed an extensive theory of muon capture in nuclei, which culminated in the elementary particle treatment put forward by C. W. Kim and himself, relying upon the use of the Goldberger-Treiman relation in complex nuclei. At the same time Primakoff examined with P. Dennery and Joseph Dreitlein rare decays of the muon, the relationship between the decays of charged and neutral Sigma hyperons, and semileptonic decays of K-mesons. With Ephraim Fischbach and other students he investigated parity-violating nuclear forces, a topic that reached back to his very first paper.
In 1969 Primakoff and Rosen returned to the problem of double beta decay. When Primakoff was asked by colleagues at the time whether the smallness of the observed neutrino masses implied or at least strongly suggested their masses were zero, he would calmly reply one should not prejudge the result; experiment would settle the matter. He wisely pointed out that what seemed natural today might not appear so in a few years. Primakoff and Halprin went on to realize that heavy Majorana neutrinos could also give rise to no-neutrino double beta decay, and in collaboration with Peter Minkowski, showed that the existing limits on the process gave rise to a lower bound on the masses of such heavy neutrinos of several times the proton mass. This is entirely consistent with the seesaw model proposed by Murray Gell-Mann, Pierre Ramond and Richard Slansky and by Tsutomu Yanagida.
Later Research Interests While always keeping a close eye on the experimental results of the day, Primakoff was also interested in broader and fundamental questions in many areas that touch physics. Toward the end of his life he wrote a review of baryon number and lepton number conservation with Rosen, a speculative paper on the chirality of electrons from beta decay and the origin of left-handed asymmetry of proteins with Alfred K. Mann and a note on testing the Pauli principle with R. D. Amado.
Primakoff was much loved as a teacher and colleague. He was encyclopedic in his knowledge and lavish in giving his time to the most senior colleague or the most junior student. For many years he taught at Penn a unique course that helped prepare graduate students for the PhD preliminary exam. Its central feature was that students would ask him questions on any subject; he would then patiently and systematically provide the answer, exploring its ramifications and extensions as he calmly worked out the solution.
Primakoff was very careful and complete in what he said and what he wrote. His lecture style and research notes were remarkable for their rococo notation and their aesthetic sense. A page would be filled with equations moving in all directions, sometimes moving back on themselves, with side remarks carefully annotating the symbols and arrows elegantly indicating the sequence in which they should be studied. At Penn pages of these handwritten research notes were the centerpieces of an art show and many colleagues still have these notes framed on their walls.
WORKS BY PRIMAKOFF
With M. H. Johnson. “Relations between the Second and Higher Order Processes in the Neutrino-Electron Field Theory.” Physical Review 51 (1937): 612–619.
With T. Holstein. “Field Dependence of the Intrinsic Domain Magnetization of a Ferromagnet.” Physical Review 58 (1940): 1098–1113.
With E. Feenberg. “Possibility of ‘Conditional’ Saturation in Nuclei.” Physical Review 70 (1946): 980–981.
With E. Feenberg. “Interaction of Cosmic-Ray Primaries with Sunlight and Starlight.” Physical Review 73 (1948): 449–469.
With S. DeBenedetti, C. E. Cowan, and W. R. Konneker. “On the Angular Distribution of Two-Photon Annihilation Radiation.” Physical Review 77 (1950): 205–212.
“Photo-Production of Neutral Mesons in Nuclear Electric Fields and the Mean life of the Neutral Meson.” Physical Review 81 (1951): 899.
“Angular Correlation of Electrons in Double Beta-Decay.” Physical Review 85 (1952): 888–890.
With W. Cheston. “‘Nonmesonic’ Bound V-Particle Decay.” Physical Review 92 (1953): 1537–1541.
With J. Bernstein, T. D. Lee, and C. N. Yang. “Effect of the Hyperfine Splitting of a μ-Mesonic Atom on Its Lifetime.” Physical Review 111 (1958): 313–315.
With S. P. Rosen. “Double Beta Decay.” Reports on Progress in Physics 22 (1959): 121–166.
“Theory of Muon Capture.” Reviews of Modern Physics 31 (1959): 802–822.
With A. Sher. “Approach to Equilibrium in Quantal Systems: Magnetic Resonance.” Physical Review 119 (1960): 178– 207.
With C. M. Andersen and A. Halprin. “Determination of the Two-Photon Decay Rate of the η Meson.” Physical Review Letters 9 (1962): 512–516.
With A. Sher. “Approach to Equilibrium in Quantal Systems. II. Time-Dependent Temperatures and Magnetic Resonance.” Physical Review 130 (1963): 1267–1282.
With C. W. Kim. “Application of the Goldberger-Treiman Relation to the Beta Decay of Complex Nuclei.” Physical Review 139 (1965): B1447–B1463.
With C. W. Kim. “Theory of Muon Capture with Initial and Final Nuclei Treated as ‘Elementary’ Particles.” Physical Review 140 (1965): B566–B575.
With A. Halprin and C. M. Andersen. “Photonic Decay Rates and Nuclear-Coulomb-Field Coherent Production Processes.” Physical Review 152 (1966): 1295–1303.
With S. P. Rosen. “Nuclear Double-Beta Decay and a New Limit on Lepton Nonconservation.” Physical Review 184 (1969): 1925–1933.
With Wen-Kwei Cheng, Ephraim Fischbach, Dubravko Tadic, and Kenneth Trabert. “Experimental Evidence from Parity-Forbidden α Decay for the Presence of Noncanceling Seagull and Schwinger Terms in Weak (Nucleon → Nucleon + Vector-Meson) Amplitudes.” Physical Review D 3 (1971): 2289–2292.
With B. Goulard. “Relation between the Energy-Weighted Sum Rules for Nuclear Photoabsorption and Nuclear Muon Capture.” Physical Review C 11 (1975): 1894–1898.
With A. Halprin, P. Minkowski, and S. Rosen. “Double-Beta Decay and a Massive Majorana Neutrino.” Physical Review D 13 (1976): 2567–2571.
With A. K. Mann. “Neutrino Oscillations and the Number of Neutrino Types.” Physical Review D 15 (1977): 655–665.
With John N. Bahcall. “Neutrino-Antineutrino Oscillations.” Physical Review D 18 (1978): 3463–3466.
With H.-Y. P. Hwang. “Theory of Radiative Muon Capture with Applications to Nuclear Spin and Isospin Doublets.” Physical Review C 18 (1978): 414–444.
With C. W. Kim. “Nuclei as Elementary Particles in Weak and Electromagnetic Processes.” In Mesons in Nuclei, edited by Mannque Rho and Denys Wilkinson, vol. 1. Amsterdam: North-Holland Publishing Company, 1979.
With R. D. Amado. “Comments on Testing the Pauli Principle.” Physical Review C 22 (1980): 1338–1340.
With A. K. Mann. “Weak Neutral Currents.” In Encyclopedia of Physics, edited by Rita G. Lerner and George L. Trigg. Reading, MA: Addison-Wesley Pub. Co., 1981.
With A. K. Mann. “Chirality of Electrons from Beta-Decay and the Left-Handed Asymmetry of Proteins.” Origins of Life and Evolution of the Biosphere11, no. 3 (1981): 255–265.
With S. P. Rosen. “Baryon Number and Lepton Number Conservation-Laws.” Annual Review of Nuclear and Particle Science 31 (1981): 145–192.
Courant, Richard, and Kurt O. Friedrichs. Supersonic Flow and Shock Waves. New York: Springer-Verlag, 1976.
“Henry Primakoff Dead at 69; Professor of Science at Penn.” New York Times, 28 July 1983.
Rosen, S. P. “Henry Primakoff: February 12, 1914–July 25, 1983.” Biographical Memoirs, vol. 66. Washington, DC: National Academy of Sciences, 1995. This DSB entry relies heavily on this memoir.
Tolman, Richard. Relativity, Thermodynamics and Cosmology. Oxford: Clarendon Press, 1934.
R. D. Amado