Baji Vinayak Thosar received PhD (1949) from Birmingham University, UK. He was Emeritus Professor and Dean, Physics Faculty, Tata Institute of Fundamental Research, Mumbai; Visiting Scientist, Niels Bohr Institute, Copenhagen (1963, 1968); and Visiting Scientist, National Science Foundation, USA (1969).

Academic and Research Achievements:Thosar had keen interest in nuclear physic, and solid state physics. During his term at the TIFR he established a very active research group in Nuclear Spectroscopy from scratch with the help of young research workers around him. He pioneered work on Positron Annihilation studies in India, specially positronium decay in molecular materials. He initiated, guided and encouraged many new research areas such as beta ray spectroscopy, borderline areas between nuclear physics and solid state physics such as moessbauer spectroscopy, positron annihilation, low temperature physics, nuclear orientation, etc. A striking example of this is the use of nuclear decay as probe to do condensed matter research, ‘Nuclear Solid State Physics’, the term often quoted by Thosar. He carried out investigations on the luminescence of ruby crystal and positron annihilation in molecular materials. Professor Thosar initiated the use of positron annihilation lifetime measurement as a tool to study solid-state physics. His group had developed the technique of measuring nuclear lifetimes using fast ?-y coincidence technique in the region of subnanoseconds. This technique was utilized in measuring lifetimes of positronium atoms in triplet state in very wide range of materials both in liquids and solids. All these studies led to the development of an empirical ‘free volume’ model to explain the correlation between the intensity and the long-lived component in the decay of ortho-positronium. The model could explain a number of results and was well accepted internationally. He also authored the book: Growing up with Science in India (1992).

Other Contributions:Thosar set up an active nuclear spectroscopy group at TIFR, Mumbai. He designed and built a new type of Beta-ray spectrometer where the focusing of charged particles was done by the electrostatic field between two coaxial metal cylinders separated by accurately machined dielectric spacer. This work was continued at TIFR where he designed and constructed a modified electrostatic spectrometer using hemispherical electrodes for focusing electrons. He served as Chairman, National Advisory Committee for International Conference on Positron Annihilation, Delhi (1985).

Awards and Honours: Professor Thosar won the Raman Centenary Gold Medal (1988). He was elected Fellow of the Indian Academy of Sciences, Bangalore and served as President, Physics Section, Indian Science Congress (1969). He was President, Maharashtra Academy of Sciences (1982-85).