IN MEMORIAM

IN MEMORIAM

Walter E. Bron

Professor of Physics and Astronomy

Irvine

1930—2002

We and others have been saddened deeply by the recent passing of Professor Walter E. Bron on November 16, 2002 at the age of 72. Walter made many key contributions to condensed matter physics, through fundamental and challenging experimental studies.

 

Walter Bron received his Ph.D. degree from Columbia University in 1959, under the direction of Art Nowick. While his thesis studies were underway, he was drafted into the U. S. Army, where he served as a research assistant in 1954-55. He was a staff member at the I.B.M. Thomas J. Watson Research Center in Yorktown Heights, NY from 1957 to 1965, followed by 19 years on the faculty of Indiana University at Bloomington. He joined our faculty at the University of California, Irvine in 1986. He was elected a fellow of the American Physical Society, and he received a Guggenheim Fellowship and the Senior Scientist Award from the Alexander von Humboldt Foundation in Germany.

 

A characteristic theme of his research involved experiments that explored novel phenomena, probed often in experiments which were innovative, and which introduced new methodologies and techniques. Many of these constituted a tour de force of experimental technique. Early in his career, he detected the first paraelectric resonance signals associated with the tunneling motions of small ions present as impurities in alkali halide crystals. He is noted as well for introducing methods to both generate and subsequently detect very high frequency phonons in solids, with frequencies in the Terahertz range, far above the frequency domain accessible to conventional ultrasonic technology. One means of generating such very high frequency phonons employed superconducting junctions both as generators and as detectors of phonon pulses. A second means was resonant pumping of vanadium ions in aluminum oxide with an infrared laser to create a population inversion, followed by stimulated emission of phonons with frequencies in the Terahertz range. A series of studies utilizing these new methods of generating very high frequency phonon pulses provided insights into new physics which is found in this regime. For instance, Walter Bron and his student J.M. O’Conner observed for the first time a “quasi diffusive” form of phonon transport that had been predicted by the Soviet theorists D.V. Kazakovtsev and Y.B. Levinson. These new techniques allowed study of other aspects of very high frequency phonon transport and interactions.

 

In the early eighties, Walter Bron turned his attention to the use of picosecond laser pulses to study diverse phenomena in the solid state in real time, through pioneering pulse-probe experiments. After his move to Irvine, he established a femtosecond laser laboratory which continued and extended these studies. During this period, he measured the non-linear optical susceptibility tensors of semiconducting materials, and completed direct studies of the decay in time of coherently generated optical phonons, polaritons, and coupled phonon/plasmon modes of doped semiconductors. In the late sixties, there was a much discussed theoretical prediction that, in the semiconducting material gallium phosphide, an acoustic phonon at the boundary of the Brilluoin zone should have an anomalously long lifetime. Walter Bron was justly proud of a very ingenious experiment which verified this prediction in 1993.

 

Walter enjoyed a warm marriage of 50 years duration with Anne, who survives him. He has two daughters, Karen and Michelle, and two granddaughters who will miss him as we will ourselves.

 

 

D. L. Mills

A. Maradudin