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DTIC ADA076100: The Effects of Velocity-Changing Collisions on Two-...
by Defense Technical Information Center
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We report the results of an experimental study of the
effects of velocity-changing collisions on two-photon and
stepwise absorption lineshapes. Excitation spectra for
the 3S(1/2) yields 3P(1/2) yields 4D(3/2) transitions of
sodium atoms undergoing collisions with foreign gas
perturbers are obtained. These spectra are obtained with
two cw dye lasers. One laser, the pump laser, is tuned
1.6 GHz below the 3S(1/2) yields 3P(1/2) transition
frequency and excites a nonthermal longitudinal velocity
distribution of excited 3P(1/2) atoms in vapor.
Absorption of the second (probe) laser is used to monitor
the steady state excited state distribution which is a
result of collisions with rare gas atoms. The spectra are
obtained for various pressures of He, Ne, and Kr gases
and are fit to a theoretical model which utilizes either
the phenomenological Keilson-Stoerer or the classical
hard sphere collision kernel. The theoretical model
includes the effects of collisionally aided excitation of
the 3P(1/2) state as well as effects due to fine-
structure state-changing collisions. Although both
kernels are found to predict lineshapes which are in
reasonable agreement with the experimental results, the
hard sphere kernel is found superior as it gives a better
description of the effects of large angle scattering for
heavy perturbers. Neither kernel provides a fully
adequate description over the entire line profile. The
experimental data is used to extract effective hard-
sphere collision cross sections for collisions between
sodium 3P(1/2) atoms and helium, neon and krypton
perturbers. (Author)
Date Published: 2017-10-25 09:48:29
Identifier: DTIC_ADA076100
Item Size: 20121644
Language: english
Media Type: texts
# Topics
DTIC Archive; Berman ,P R ; NEW YORK...
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