The general quantum treatment of collisions of a 2Σ+ molecule with hyperfine structure is presented. The recoupling technique introduced by Corey and McCourt into the field of molecular collisions [J. Phys. Chem. 87, 2723 (1983)] allows us to represent hyperfine‐state‐resolved tensor opacities, and hence cross sections, in terms of the corresponding nuclear‐ and also electron‐spin‐free quantities. The formalism also predicts (independent of the dynamical limit) that the largest F→F′ cross sections will be those for which ΔF=ΔJ, a rule well known for radiative transitions. Hyperfine‐state‐resolved scattering involving collisions of CaBr(X 2Σ+) with Ar is also studied here experimentally by electric quadrupole state selection and cw dye laser fluorescence detection. The relative final F′ distributions were determined for the N=3,e→N=5,e and N=2,e→N=1,e collisional transitions. These results clearly exhibit the ΔF=ΔJ propensity rule. Moreover, the F′ distributions were predicted with nearly quantitative accuracy using our previously determined CaCl(X 2Σ+)‐Ar tensor opacities. By contrast, the MJ‐ randomization model, first proposed to treat the influence of hyperfine structure in atomic collisions, is shown to disagree with both our experimental data and theoretical predictions.
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1 September 1985
Research Article|
September 01 1985
Collision‐induced transitions between molecular hyperfine levels: Quantum formalism, propensity rules, and experimental study of CaBr(X 2Σ+)+Ar
Millard H. Alexander;
Millard H. Alexander
Department of Chemistry, University of Maryland, College Park, Maryland 20742
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Paul J. Dagdigian
Paul J. Dagdigian
Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218
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Millard H. Alexander
Paul J. Dagdigian
Department of Chemistry, University of Maryland, College Park, Maryland 20742
J. Chem. Phys. 83, 2191–2200 (1985)
Article history
Received:
April 02 1985
Accepted:
May 15 1985
Citation
Millard H. Alexander, Paul J. Dagdigian; Collision‐induced transitions between molecular hyperfine levels: Quantum formalism, propensity rules, and experimental study of CaBr(X 2Σ+)+Ar. J. Chem. Phys. 1 September 1985; 83 (5): 2191–2200. https://doi.org/10.1063/1.449311
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