Up: Rovibrational excitation of HD
Pure rotational transitions of HD have been detected recently. In the
dense photon
dominated region of the Orion bar the R(0) line at 112 m
has been
detected with the long wavelength
spectrometer (LWS) of ISO (Wright et al. [1999]) and Bertoldi et al.
([1999]) report the detection of the R(5) line at 19.43
m
with the short wavelength spectrometer (SWS) of ISO in the Orion molecular
outflow. On the other hand, infrared rovibrational transitions in
HD have been predicted by Sternberg ([1990]) and Timmermann
([1996]) as possible occurrences in dense photon dominated regions
(PDR). The interpretation of such observations require the knowledge of
the different microscopic processes involved and in particular the
rovibrational excitation rate coefficients due to the various perturbers, i.e.
atomic and molecular hydrogen as well as helium. In a previous paper, Roueff
& Zeippen ([1999]) have calculated the rotational excitation of HD due
to collisions with helium. In the present work, these calculations are extended
to the rovibrational excitation of HD by helium. Note that rovibrational
excitation of HD by hydrogen atoms and molecules has already been calculated by
Flower & Roueff ([1999]) in a complete close-coupling quantal approach.
The same method is used in this study. Section 2 of the present paper
summarizes the formalisms selected for the calculations. Results are given in
Sect. 3 and a discussion plus a conclusion can be found in Sect. 4.
Up: Rovibrational excitation of HD
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