Browsing by Author "Chandra, S."

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    About the Dunham coefficients Y20 and Y11 for diatomic molecules
    (2001-01-12) Sharma, A. K.; Chandra, S.
    For a diatomic molecule, when the Dunham coefficients Y20 is negative, all fea- tures of potential-energy curve can be reproduced. When Y20 is positive; it is not possible to reproduce all features of the potential-energy curve. However, turning points for some lower vibrational states can be obtained.
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    Another suggestion for an interstellar C5H2 search
    (2005-07-01) Chandra, S.; Shinde, S. V.; Musrif, P. G.
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    Collisional rates for vib-rotational transitions in diatomic molecules
    (2001-06-24) Chandra, S.; Sharma, A. K.
    A number of diatomic molecules have been found in vibrationally excited states in several cosmic objects. The molecules in vibrationally excited states provide valuable information about the physical conditions prevailing near star forming regions and in circumstellar envelopes of late-type stars. To analyze the spectrum of such molecules, some of the important parameters required are the collisional rate coe cients for vib-rotational transitions in the molecule. Currently, knowledge of collisional rate coe cients is very poor. Here, we discuss a method for calculating the collisional rate coe cients for vib-rotational transitions in a diatomic molecule, where the colliding partner H2 is considered as a structureless particle. This method is quite good for high temperatures (usually found in star-forming regions and in circumstellar envelopes of late-type stars), but may be questioned for low temperatures. As an example, calculations for the CS molecule at 500 K for three vibrational states are presented.
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    Suggestions for an interstellar cyclopropene search
    (2001-07-05) Sharma, A. K.; Chandra, S.
    Following tentative detection of cyclopropene (C3H4) in Sgr B2 through its transition 322−221, several attempts to con rm the presence of cyclopropene in astronomical objects (including Sgr B2 itself) have been made. We suggest that cyclopropene may be observed in astronomical objects through its transition 220−221 at 3.67218 GHz, in absorption, even against the cosmic 2.7 K background, in a region having low density and low kinetic temperature.