Clifford V. Heer

Abstract

Clifford V. Heer, a noted researcher in low-temperature, statistical, and laser physics, died 8 July 2004 in Columbus, Ohio, of complications from Parkinson’s disease.Heer was born 31 May 1920 in Burlington, Ohio. He received a BSc in engineering physics at Ohio State University in 1942. From 1942 to 1946, he served as a lieutenant in a radar unit with the US Army Signal Corps in the South Pacific. He returned to OSU and presented his PhD thesis, “Some Properties of Superconductors Below 1 K” in 1949, under the supervision of John Daunt. Heer became an assistant professor in OSU’s department of physics and astronomy in 1949, a full professor in 1961, and retired as professor emeritus in 1990.Heer’s early research was in low-temperature physics, a field in which he made several outstanding contributions. In 1949, he and Daunt were the first to describe what is now called a superconducting thermal switch, which uses the increase in thermal conductivity when a superconducting metal is made normal by a magnetic field. Their proposal was based on their own measurements on titanium below 1 K. They proposed using such switches in a cyclic magnetic refrigerator. Heer and Daunt also made notable advances in the study of mixtures of liquid helium-3 with helium-4. What is now known as the Heer–Daunt model shows that many thermodynamic properties of liquid mixtures closely resemble those of coexisting Bose and Fermi ideal gases. In addition to his experiments on helium mixtures, Heer made extensive measurements of superconducting critical fields, low-temperature specific heats of metals, and magnetic susceptibilities in paramagnetic solids.During the latter part of the 1950s, Heer’s research shifted from low-temperature physics to the study of electromagnetic waves. While working as a consultant at Space Technology Laboratories Inc in Los Angeles, he proposed and carried out a measurement of absolute rotation based on the beat frequency that results from the splitting of a degenerate mode in a rotating resonant cavity. The optical detection of rotation was well known as the Sagnac effect, but Heer was the first to convert the small difference in effective path length due to rotation into the frequency domain, where it could be measured with high sensitivity and accuracy. The invention of the laser allowed such a measurement at optical wavelengths with even higher sensitivity. Such interferometers, now commonly referred to as laser gyroscopes, operate on the principle described by Heer in a patent disclosure in 1959 and discussed at an American Physical Society (APS) meeting in January 1961. (See Heer’s letter to Physics Today, May 1982, page 134)In the early 1960s, Heer suggested a method of confining particles that have a magnetic dipole moment, such as spin-polarized hydrogen or very cold neutrons, in a magnetic bottle. A decade or so of research revealed that it was possible to obtain thermal moderation of neutrons to temperatures of the order of 10−2 to 10−3 K, and Heer’s method became practical.From the 1960s into the early 1980s, Heer continued his interest in laser physics. Before the wide availability of commercial lasers, he and his students built a carbon dioxide laser and studied photon echoes in sulfur tetrafluoride and sulfur hexafluoride gases. Insights from those experiments led to the study of electron-beam pumped superradiance in nitrogen, and from there to the fabrication of nitrogen-laser pumped dye lasers, instruments that enabled Heer’s group to examine coherent phenomena in atomic sodium vapor. He predicted, and later confirmed experimentally, unique focusing properties of photon echoes in that system.Heer was keenly interested in the relatively new field of nonlinear optics, and he and his students applied their experience with sodium vapor to studying sum-frequency generation in that material, using simultaneous pumping with two dye lasers and making use of the sharp atomic resonance lines to enhance the optical nonlinearity. Combining that nonlinear effect with coherence effects, Heer’s group then studied the optical properties of photon echoes that have been stimulated by three frequencies.Heer also made significant theoretical contributions to other fields of physics, including the localization of orthopositronium in gases and the effect of weak neutral currents on cosmic hydroxyl.Among Heer’s published works are the textbook Statistical Mechanics, Kinetic Theory and Stochastic Processes (Academic Press, 1972), several laboratory manuals, and numerous publications on low-temperature physics, atomic and laser physics, general relativity, and statistical physics. He was a consultant for TRW Inc, Space Technology Laboratories, and Honeywell, and a technical consultant for the US Justice Department. In 1990, the Ohio section of APS honored him with the William Fowler Award. Colleagues remember Heer with affection. Among the OSU physics faculty, he was known as a man of principle who did not hesitate to express his candid opinion when necessary. Sometimes his was the only dissenting vote in faculty meetings when a decision more convenient than honorable was being considered.His interests outside of the university involved his great love of the outdoors. He led Boy Scouts on camping and canoeing trips and was an avid hiker and gardener. After retirement, he and his wife traveled extensively in South America, Australia, New Zealand, Egypt, and Turkey. Clifford V. Heer PPT|High resolution© 2005 American Institute of Physics.