Mikael Levonovich Ter-Mikaelian, an important contributor to high-energy physics, laser physics, and nonlinear optics, died on 31 January 2004 in Yerevan, Armenia, from complications following gallbladder surgery.
Ter-Mikaelian was born in Tbilisi, Georgia, on 10 November 1923. His father, a railway engineer in czarist and Bolshevik Russia, published works on Fermat’s problem and was the minister of communications in the first Republic of Armenia. His mother schooled him in music and languages, especially French. After his father’s death in 1943, he, his mother, and his brother moved to Yerevan.
A graduate of the Yerevan State University (YSU) in 1948, he received a diploma in physics and mathematics. He went to Moscow, where he completed his candidate dissertation at the Lebedev Physical Institute in 1953 under the supervision of Evgeny Feinberg. During that period, he made the most important discovery of his career: the coherence-length effect in high-energy particle interactions with matter. He showed that with the increase of energy, the longitudinal size of the particle-matter interaction region increases to macroscopic dimensions even though the wavelength of radiation produced by the particles is shorter than the interatomic distances. As a result, the cross sections of bremsstrahlung and photon pair production are enhanced at high energies. His results have since found wide application in the fields of high-energy particle and radiation physics.
From 1954 to 1963, he was affiliated with the Yerevan Physics Institute (YerPhI), first as the head of the theoretical department, and then as the institute’s deputy director. In 1954, he predicted that, due to the polarization of the medium, the Bethe–Heitler bremsstrahlung spectrum would be suppressed at certain photon energies. This phenomenon, now known as the Ter-Mikaelian or longitudinal density effect, resembles the Fermi density effect. During 1960–61, Ter-Mikaelian developed the theory of x-ray transition radiation produced in a stack of plates. He and his colleagues showed that XTR could be used to identify and measure the energy of single particles with energies much higher than is possible with čerenkov detectors. XTR detectors first developed at YerPhI are now used in high-energy physics experiments all over the world. In 1962, Ter-Mikaelian received his doctorate in physics and mathematics from the Lebedev Institute.
His classic monograph High-Energy Electromagnetic Processes in Condensed Media, published in 1969 in Russian and in 1972 in English (Wiley-Interscience), has served as a virtual handbook on radiation processes since its publication. One of the most cited books in the field, it is famous for its clear exposition and breadth and depth of discussion. Among the many important subjects examined in that book is the radiation emitted by electrons passing through the planes of a crystal. In this process, the Weizsäcker–Williams pseudo-photons accompanying the electron are diffracted and emitted as real photons at angles close to the Bragg angle. This radiation was later “rediscovered” by other theorists and termed quasi Čerenkov or parametric x-ray radiation.
In 1963, Ter-Mikaelian left YerPhI and began new activities in quantum electronics at YSU. As the dean of the physics department, he founded four new chairs and organized the Joint Radiation Laboratory of the YSU and the Academy of Sciences of Armenia (ASA). Under his supervision, that laboratory produced the first solid-state lasers in the Soviet Union and, in 1968, became the Institute for Physical Research (IFI) of the ASA.
From 1968 to 1994, Ter-Mikaelian was director of IFI. For part of that time (1988–94), he served as academician-secretary of the ASA’s department of physics and mathematics. He retired from IFI in 1994 and became honorary director of that institute; he also was appointed head of IFI’s theoretical department, a position he held until his death.
The works of Ter-Mikaelian and his team at IFI were the basis of the monograph, written with Andrey Mikaelian and Yuri Turkov, entitled Solid-State Optical Generators (Soviet Radio, 1967)—the first book on laser physics in the Soviet Union. Even today, it is an extremely useful tool for physicists and engineers.
For their work in the field of quantum electronics and their initiatives in the industrial production of lasers and laser materials, Ter-Mikaelian and his associates were awarded the State Award of Armenia in 1980. They investigated new phenomena such as self-induced population inversion, three-component structure in resonance fluorescence, and two-photon effects on “dressed atoms.” That work and studies of resonant interaction of laser radiation with atomic systems established Armenia as a world-class contributor to the field of laser physics and nonlinear optics. In his final years, Ter-Mikaelian revisited the field of high-energy radiation physics and had begun work on the second edition of his world-famous book.
Ter-Mikaelian was an academician of the ASA and received many honors in his career. But the most important accolades for him were the love and respect of the many scientists who flourished under his supervision.
Because of his high intelligence, significant scientific achievements, administrative leadership, personal charm, and good humor, Ter-Mikaelian is highly revered and mourned by his fellow Armenians and by the international scientific community at large. His many friends worldwide remember and greatly miss him.
