Raj Gupta has been elected a Fellow of the American Physical Society
"for the first Doppler-free spectroscopy of the optically inaccessible
states of alkali atoms, for the most complete study of photothermal
technique in flowing fluids, and for innovative use of photothermal
technique to combustion diagnostics." He joins Professors Ray Hughes,
Art Hobson, and William Harter as the Department's fourth APS Fellow.
During 1970-78, in collaboration with William Happer at Columbia
University, Gupta developed new Doppler-free spectroscopic techniques
to reach the optically inaccessible states (the states that cannot
be excited directly from the ground states) of the alkali atoms, and
performed the first high-resolution measurements on these states.
These measurements revealed inverted hyperfine structures in
certain states and led, for the first time, to understanding the role
of many-body effects in these simple single-valence-electron atoms.
After joining the University of Arkansas in 1978, Gupta proposed
and successfully applied photoacoustic and photothermal techniques
to combustion diagnostics. This was a new idea, radically different
from anything else in use (e.g., laser induced fluorescence on coherent
anti-Stokes Raman spectroscopy), and generated considerable interest
in the combustion diagnostics community. Raj has also done extensive
work on the development of the photothermal technique itself. He was
one of the first to apply this technique to flowing media and has
performed, in collaboration with UA colleague Reeta Vyas, the most
complete study of the generation and evolution of photothermal signals
in flowing fluids. This work has found applications in such diverse
areas as anemometry, smoke detection in exhausts, pollution measurements,
combustion diagnostics, laser-induced plasma diagnostics, and chemical
analysis in flowing media.*
