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Proceedings Paper

How collisions cause misalignment: alignment decay in acetylene 21
Author(s): Joshua B. Halpern; Ralf Dopheide; Helmut Zacharias
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Paper Abstract

Strongly aligned samples of C2H2 were prepared in several rotational states of the 21 level by stimulated Raman pumping. The effects of acetylene self-collisions on alignment have been studied in detail. Laser induced fluorescence was used to verify the initial degree of alignment and follow its decrease via collisions. Measurements of the initially excited alignment agree well with theoretical calculations of that achievable by stimulated Raman pumping and the decay can be modeled by a simple kinetic scheme based on the selection rule (Delta) M equals 1. As the rotational quantum number increases, there is decrease in the alignment decay rate, but a rapid increase in collisional transfer from a particular MJ level to its nearest neighbors. The physical basis for these trends is discussed. Transfer of alignment to other angular momentum levels by inelastic collisions has been observed when (Delta) J equals 2, but is absent when (Delta) J is greater than 2. These experiments can be analyzed to yield an average angular change during a collision where (Delta) J equals 2.

Paper Details

Date Published: 18 September 1995
PDF: 8 pages
Proc. SPIE 2548, Laser Techniques for State-Selected and State-to-State Chemistry III, (18 September 1995); doi: 10.1117/12.220868
Show Author Affiliations
Joshua B. Halpern, Howard Univ. (United States)
Ralf Dopheide, Univ. Essen (Germany)
Helmut Zacharias, Univ. Essen (Germany)

Published in SPIE Proceedings Vol. 2548:
Laser Techniques for State-Selected and State-to-State Chemistry III
John W. Hepburn, Editor(s)

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