How collisions cause misalignment: alignment decay in acetylene 21

Joshua B. Halpern; Ralf Dopheide; Helmut Zacharias

doi:10.1117/12.220868

18 September 1995 How collisions cause misalignment: alignment decay in acetylene 2¹

Joshua B. Halpern, Ralf Dopheide, Helmut Zacharias

Proceedings Volume 2548, Laser Techniques for State-Selected and State-to-State Chemistry III; (1995) https://doi.org/10.1117/12.220868
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

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 M_J 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.

Citation Download Citation

Joshua B. Halpern, Ralf Dopheide, and Helmut Zacharias "How collisions cause misalignment: alignment decay in acetylene 2¹", Proc. SPIE 2548, Laser Techniques for State-Selected and State-to-State Chemistry III, (18 September 1995); https://doi.org/10.1117/12.220868

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