Lawrence Marvin Langer, an early leader in experimental tests of the theory of nuclear beta decay, and in studies of neutrino properties, died on 17 January 2000 in Bloomington, Indiana, after a long battle with multiple sclerosis.
Langer was born in New York City on 22 December 1913. He received three physics degrees from New York University: his BS in 1934, MS in 1935, and PhD in 1938. The same year he earned his doctorate, he went to Indiana University as one of four new faculty members hired to start a modern research program. He contributed to the construction of a cyclotron, and applied the beta–gamma coincidence method to the study of the energy levels of atomic nuclei.
As World War II approached, Langer was recruited to work in the MIT Radiation Laboratory, where he was very much involved in flight-testing of radar prototypes in fighter planes. He was then called by the US Navy to San Diego, where he worked on the development and testing of sonar detectors. In 1943, he was invited to Los Alamos, where he worked on developing and testing the “gun” mechanism used to set off the uranium-235 bomb. He accompanied the weapon to the western Pacific island of Tinian, where he supervised its final assembly.
In 1946, he returned to the Indiana University faculty and developed one of the world’s major laboratories for the study of beta-ray spectra shapes and other work in nuclear spectroscopy. Langer’s ingenuity as a physicist was evident in the way he improved instruments and carried out experiments. He was among the earliest physicists to use a shaped-magnetic-field spectrometer to study spectrum shapes, and was a leader in source and detector techniques.
In the late 1940s and early 1950s, Langer and his students made important contributions to confirming the Fermi theory of beta decay for “allowed” transitions. In 1949, he and his student H. Clay Price found the first clear example of a “uniqueforbidden” shape. In 1952, he and his student R. Douglas Moffat set a significant upper limit on the mass of the neutrino from studies of the beta spectrum of tritium near its end-point. He returned often to neutrino-related studies, including questions of neutrino–antineutrino identity, a search for neutrino degeneracy, and further studies of neutrino mass. He did some of this work as a consultant, working with collaborators at Los Alamos. Langer and his students also made important contributions to the knowledge of the systematic features of nuclear energy levels, and thus to the confirmation of the nuclear shell and rotational models.
Langer’s work on beta decay and nuclear structure showed the advantage of close collaboration between experiment and theory. His work was influenced by that of his colleague in theoretical physics, Emil Konopinski, and vice versa. Their 1953 Annual Review article on what was then known about beta decay was widely cited.
Langer supervised 27 students through their PhD work. For many years, his research group was the largest in the Indiana University physics department, and was known to be exceptionally lively and productive. He set an example through his enthusiasm and commitment to research; many of his students went on to have distinguished careers. Langer was also a stimulating teacher of undergraduates, known especially for his vivid lecture demonstrations.
Langer became chair of the Indiana University physics department in 1965 and played a major role in more than doubling the size of the department and introducing new research areas through an NSF Science Development Program. Simultaneously, he was deeply involved in establishing and staffing the innovative Indiana University Cyclotron Facility and Nuclear Theory Center as part of the NSF program.
Langer stepped down as chair in 1973, returning to full-time teaching and research. He retired from Indiana University in June 1979, and was unable to continue research because of his deteriorating physical condition.
Langer greatly enjoyed his life in southern Indiana and his time in New Mexico. His students remember him as a mentor who inspired them always to seek definitive answers to crucial physics questions. He was a man of good humor and personal warmth, with a mental sharpness and an enduring smile.
