Walter Ernest Bron, who made key contributions to condensed matter physics through fundamental and challenging experimental studies, died on 16 November 2002 in Irvine, California.Walter was born in Berlin, Germany, on 17 January 1930, and his family moved to the US from Amsterdam in 1939 to flee the Holocaust. He received his bachelor of mechanical engineering degree from New York University in 1952 and his MS in metal science in 1953 from Columbia University. He continued at Columbia and earned his PhD in physics in 1959 under the direction of Art Nowick. His thesis explored the bleaching of color centers in alkali halides by x rays. While his thesis studies were under way, he was drafted into the US Army. He served as a research assistant at the Army Research Laboratory in Fort Belvoir, Virginia, from 1954 to 1956.After leaving the army in 1957, Walter joined IBM Corporation’s T. J. Watson Research Center in Yorktown Heights, New York, as a research associate. He was promoted to research physicist in 1958 and remained in that position until 1966. During the 18 years that followed, he served on the physics faculty of Indiana University. He then joined the physics faculty at the University of California, Irvine, in 1986.Characteristic of his research were experiments that explored novel phenomena and introduced new methodologies and techniques. Many of those experiments constituted a tour de force of experimental technique. During the mid-1960s, he detected the first paraelectric resonance signals associated with the tunneling motions of small ions present as impurities in alkali halide crystals. He introduced methods to both generate and subsequently detect very high-frequency phonons in solids, with frequencies in the THz range, far above the frequency domain accessible to conventional ultrasonic technology. One means by which he generated such very high-frequency phonons was using superconducting junctions both as generators and as detectors of phonon pulses.Using another approach, resonant pumping of vanadium impurities in aluminum oxide with an infrared laser, he created a population inversion and then stimulated emission of phonons with frequencies in the THz range. That work provided insights into the physics of very-high-frequency phonons. In 1982, Walter and his student J. M. O’Conner observed for the first time a quasi-diffusive form of phonon transport that had been predicted by Soviet theorists D. V. Kazakovtsev and Y. B. Levinson.During the early 1980s, Walter turned his attention to using 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 that continued and extended those studies. During this period, he measured the nonlinear 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 1993, Walter conducted an ingenious experiment that verified a theoretical prediction discussed actively during the late 1960s. The prediction was that, in the semiconducting material gallium phosphide, an acoustic phonon at the boundary of the Brillouin zone should have an anomalously long lifetime. Walter was justly proud of his experiment, which verified this long-standing prediction.Among his professional honors, Walter received a Guggenheim Fellowship in 1966 from the John Simon Guggenheim Memorial Foundation. In 1973, he received the Senior Scientist Award from the Alexander von Humboldt Foundation in Germany.Walter and his wife enjoyed a warm marriage of 50 years. He has two daughters and two granddaughters who will miss him as we will. Walter Ernest Bron PPT|High resolution© 2003 American Institute of Physics.
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