OODR SPECTROSCOPY OF BaO: VELOCITY ANALYZED ROTATIONAL RELAXATION
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Date
1978
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The technique of sub-Doppler optical-optical double resonance spectroscopy is used to probe one velocity component of rotationally relaxed $^molecules^{1,2}$. The process is $4\leftarrow 3\leftarrow 2\leftarrow1:$ co-propagating 1 MHz bandwidth cw dye lasers excite the $4\leftarrow3$ and $2\leftarrow1$ transitions and $3\leftarrow2$ rotational relaxation in the intermediate vibronic level is sampled. For out experiments on BaO (in a 1 torr $Ba + CO_{2} + $Ar flame) the dye lasers excite C-A (3,1) and A-X (1,0) bands. Velocity distributions along the propagation direction (z) of the $2\leftarrow1$ laser are sampled in the optically pumped and collisionally relaxed levels as function of $J, \Delta J, v_{z}$, and Ar pressure. No $\Delta J$ propensity rule is observed. The single collision rotation-ally inelastic cross-section is approximately 10{\AA}$^{2}$ and no $v_{z}$ dependence has been, detected. When molecules with $v_{z} = 0$ are rotationally transferred the line width increases (but remains sub-Doppler), corresponding to either an increase in total velocity or a reorientation of transverse velocity. Linewidths increase monotonically with $\Delta $J. When $v_{z}$ is selected such that $v_{z} >> (v_{X}, v_{y})$, rotationally relaxed levels appear with asymmetric lines skewed toward $v_{z} = 0$ in the $C\leftarrow A$ excitation spectrum.
Description
$^{1}$J. L. Kinsey, J, Chem. Phys. 66, 2560 (1977). $^{2}$W. D. Phillips and D. Pritchard, Phys. Rev. Lett. 33, 1254 (1974).""
Author Institution: Laboratoire de Spectrom\'etrie Ionique et Mol\'eculaire, Universit\'e de Lyon (I); Department of Chemistry, Massachusetts Institute of Technology
Author Institution: Laboratoire de Spectrom\'etrie Ionique et Mol\'eculaire, Universit\'e de Lyon (I); Department of Chemistry, Massachusetts Institute of Technology