Herman Feshbach, a leader in the field of nuclear physics from the 1940s to the end of the century, died on 22 December 2000 in Cambridge, Massachusetts, of congestive heart failure. He was renowned and respected for his seminal work in nuclear theory, his leadership in the international physics enterprise, and his commitment to world peace and human rights.
Born in New York City on 2 February 1917, Herman received his SB in 1937 from the City College of New York, with his lifelong friend Julian Schwinger as a classmate. Herman obtained his PhD in physics at MIT in 1942. His thesis, under the supervision of Philip Morse, approximately derived the properties of tritium from nuclear forces, a difficult task at the time. Herman remained at MIT, rising through the ranks to institute professor in 1983. He also was a founder and director of MIT’s Center for Theoretical Physics from 1967 to 1973 and head of the physics department from 1973 to 1983.
In 1954, Herman, Charles Porter, and Victor Weisskopf developed the cloudy crystal ball model, which revolutionized the treatment of nuclear reactions, initially providing a detailed description of the scattering of neutrons from nuclei. The model’s characterization of the nucleus as a complex “optical” potential combines the independent nucleon aspect embodied in the shell model with the excitation of dense compound nuclear levels postulated by Niels Bohr to explain many aspects of nuclear reactions.
Herman’s subsequent (1958) development of a general nuclear reaction theory, based on the projection of the nuclear state into direct and compound channels, resulted in such intuitive and important concepts as doorway states and multistep reactions. These methods are the backbone of complex nuclear reaction calculations today. A specific application of this theory is the inelastic multichannel Feshbach resonance, which is now of importance in atomic Bose–Einstein condensation.
The compound nucleus channels require a statistical description of the level distribution, a subject to which Herman gave much attention. With Arthur Kerman and Steven Koonin, he developed during 1977 to 1980 a statistical treatment of multistep compound and direct reactions. In the years just preceding his death, this research was extended, with Alfredo Molinari and others, to the properties of nuclear matter by developing a statistical theory of the mean field.
Herman, with Kerman in 1966, noted that recoilless (K−, π −) reactions would efficiently produce heavy hyper-nuclei. As a result of this finding, Harry Palevsky and Robert Chrien initiated experimental programs.
Eugene Wigner’s R-matrix theory is frequently used to express the effect of the degrees of freedom appropriate within the nuclear radius on the longer range wavefunction. Herman realized that this separation into two regions connected by a boundary condition was relevant to the interactions of hadrons. He successfully interpreted, with one of us (Lomon), the nucleon forces up to intermediate energies in this way. Because of the simple properties of quantum chromodynamics at short distances, the R-matrix method can incorporate the quark and gluon degrees of freedom in hadron reactions.
Herman, together with Francesco Iachello, initiated another and very different approach to nuclear structure and reactions in the interacting boson model in which the large number of single fermion degrees of freedom are approximated by a few bosonic degrees of freedom. Since the formulation of this approach in 1973, there have been extensions to nuclei with an odd atomic number and the powerful use of dynamic symmetries. Herman expected the model to be more limited in scope; he watched its later successes bemusedly from the sidelines.
The role of symmetries in nuclei always intrigued Herman. Beyond the many well-known applications of rotational symmetry, Herman considered the effect of SU(3) symmetry in hyper-nuclei. In particular, he showed, with Carl Dover in 1987, that the symmetry could lead to observable widths of Σ hyper-nuclei despite the expected rapid transition to a Λ hyper-nucleus. In the last year of his life, he applied his reaction theory, together with Mahir Hussein, Kerman, and Oleg Vorov, to understanding the large parity violations seen in thermal neutron reactions in heavy nuclei as being due to the coherent effects of the doorway states, and predicting the effects of time-reversal symmetry breaking.
Herman’s great service to physics was not limited to research. Many of his students are well known and respected in the field. His leadership in the MIT physics department extended to national and international physics. In the 1960s, he, Allan Bromley, and Heinz Barschall organized the American Physical Society’s division of nuclear physics, which he chaired from 1970 to 1971. In 1969, he was elected into the National Academy of Sciences. He was a consultant to the White House Office of Science Policy in the early 1970s. An initiator of the nuclear science advisory committee to the US Department of Energy and NSF, he was its first chairman from 1979 to 1982. He was president of APS in 1981 and president of the American Academy of Arts and Sciences from 1982 to 1986.
In the 1990s, Herman was persuaded by Bromley to chair the nuclear physics commission of the International Union of Pure and Applied Physics. As chair, he organized an international meeting on nuclear physics in Amsterdam with the goal of improving international cooperation for nuclear facilities. It was a politically difficult meeting; Bromley, who was the keynote speaker, remembers that Herman, with his usual diplomacy and flair (including a display of temper that only his close friends recognized to be totally simulated), brought the meeting to a peaceful and constructive close. Herman also served on the boards of governors of the Weizmann Institute of Science (1978–95) and Tel Aviv University (1987–90).
Herman’s publications affected physics. Generations of physicists—and engineers—fueled their mathematical tool kits from Morse and Herman’s Methods of Theoretical Physics, whose first edition was published in 1953 and the most recent edition, in 1999 (McGraw-Hill). He put much of his energy into modernizing these volumes, including adding a chapter on group theory and its applications. Unfortunately, he did not complete this task before his death. His book, with Amos de Shalit, called Theoretical Nuclear Physics (Wiley, 1974), is one of the classics in the field; Herman wrote the sequel, Theoretical Nuclear Physics: Nuclear Reactions (Wiley, 1992), which deserves similar status.
Herman’s impact on the physics literature went beyond his own writings. In 1957, he and Morse, in reaction to the splitting of the Physical Review into subfields and the publication’s constraints on lengthy articles, founded the Annals of Physics to publish a range and depth of material. Herman succeeded Morse as chief editor.
Passionate about human welfare and rights and about the folly of war, Herman put his energy and talents into rectifying wrongs. He played a critical role in the founding of the Union of Concerned Scientists, served as its first chair, and continued to support it, especially on nuclear arms control. He pursued similar goals as chairman of the APS panel on public affairs (1976–78). In 1980, as APS president, he established a human rights committee to intervene in support of oppressed physicists in the Soviet bloc, Argentina, and Chile, and made major personal efforts on behalf of the dissidents and refuseniks. Of special interest was his fight for the freedom of Andrei Sakharov. On another front, he was instrumental in improving the position of women and minorities in physics and academia.
Herman’s fervor for physics and people endeared him to his colleagues, even if his fierceness on behalf of his causes may have sometimes distressed them. He will be sorely missed by the physics community and his many friends.
