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Astron. Astrophys. Suppl. Ser. 142, 113-118

Collisional rates for asymmetrical top molecules

S. Chandra - W.H. Kegel

Send offprint request: W.H. Kegel

Institut für Theoretische Physik der Johann Wolfgang Goethe Universität Frankfurt, Robert-Mayer-Str. 8-10, D-60054 Frankfurt am Main 11, Germany
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Received May 10; accepted December 13, 1999

Abstract:

Collisional rate coefficients for rotational transitions in C₃H₂ and SiC₂ due to collisions with H₂ molecules are calculated. The C₃H₂ has two distinct species, ortho and para, whereas the SiC₂ has only ortho specie due to spin statistics for the identical carbon nuclei. For ortho- and para-C₃H₂ we accounted for 47 and 48 energy levels, respectively. The calculations are done for the kinetic temperatures 30, 60, 90, and 120 K. For ortho-SiC₂, we accounted for 40 energy levels and the calculations are done for the kinetic temperatures 25, 50, 75, 100, and 125 K. The results are reported here for the transitions in the upward direction. The values for the downward direction can easily be calculated with the help of the detailed equilibrium equation.

Key words: ISM: interstellar molecules -- molecular data