Rotational relaxation in supersonic beams of hydrogen by high resolution photoelectron spectroscopy

The rotational relaxation of n-H2, p-H2, HD, and n-D2 in a free jet expansion was studied by means of rotationally resolved photoelectron spectroscopy using a collimated supersonic molecular beam. Rotational state distributions were determined from the relative intensities of the Q branch rotational...

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Bibliographic Details
Published in:The Journal of chemical physics 1982-11, Vol.77 (10), p.4818-4825
Main Authors: Pollard, J. E., Trevor, D. J., Lee, Y. T., Shirley, D. A.
Format: Article
Language:English
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Summary:The rotational relaxation of n-H2, p-H2, HD, and n-D2 in a free jet expansion was studied by means of rotationally resolved photoelectron spectroscopy using a collimated supersonic molecular beam. Rotational state distributions were determined from the relative intensities of the Q branch rotational components for a wide range of stagnation pressures with nozzle temperatures from 300 to 700 K. Significant deviations from a Boltzmann distribution were observed for those cases in which the degree of rotational relaxation was substantial. HD was found to relax after undergoing only one-tenth of the number of collisions required to relax H2 or D2. The state-to-state rate constants method of Rabitz and Lam was used to model the relaxation of p-H2 and was confirmed to be quite effective in accounting for the experimentally observed population distributions.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.443722