Effects of velocity-changing collisions on two-photon and stepwise-absorption spectroscopic line shapes
We report the results of an experimental study of the effects of velocity-changing collisions on two-photon and stepwise-absorption line shapes. Excitation spectra for the 3S/sub 1/2/ ..-->.. 3P/sub 1/2/ ..-->.. 4D/sub 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/sub 1/2/ ..-->.. 3P/sub 1/2/ transition frequency and excites a nonthermal longitudinal velocity distribution of excited 3P/sub 1/2/ atoms in the 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/sub 1/2/ state as well as effects due to fine-structure state-changing collisions. Although both kernels are found to predict line shapes 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/sub 1/2/ atoms and helium, neon, and krypton perturbers.
- Research Organization:
- Bell Laboratories, Holmdel, New Jersey 07733
- OSTI ID:
- 5449076
- Journal Information:
- Phys. Rev., A; (United States), Vol. 21:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATOM-ATOM COLLISIONS
ENERGY-LEVEL TRANSITIONS
HELIUM
KRYPTON
NEON
SODIUM
ABSORPTION SPECTROSCOPY
DISTRIBUTION
LINE WIDTHS
VELOCITY
ALKALI METALS
ATOM COLLISIONS
COLLISIONS
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
METALS
NONMETALS
RARE GASES
SPECTROSCOPY
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena