Suggestion for Search of Malononitrile (CH 2 (CN) 2 ) in a Cosmic Object: Potential Spectral Lines
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uggestion for Search of Malononitrile (CH2(CN)2) in a Cosmic Object: Potential Spectral Lines1 M. K. Sharmaa, *, M. Sharmab, **, and S. Chandrac, *** aAmity
Centre for Astronomy and Astrophysics, Amity Institute of Applied Sciences, Amity University, U.P., India b S.O.S In Physics, Jiwaji University, India c Amity Centre for Astronomy and Astrophysics, Amity Institute of Applied Sciences, Amity University, U.P., India *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] Received July 12, 2019; revised May 30, 2020; accepted May 30, 2020
Abstract—Though accurate laboratory studies of malononitrile (CH2(CN)2), a dinitrile molecule, have been carried out from time to time, and it has large electric dipole moment μ = 3.735 D, its detection in a cosmic object is still awaited. Because of two equivalent hydrogen atoms, it has ortho and para species. In order to obtain information about some potential spectral lines of malononitrile, which may play important role for its identification in a cosmic object, we have carried out Sobolev large velocity gradient (LVG) analysis, using spectroscopic data, for each of the species. We have calculated energies of 250 lower rotational levels (up to 98 cm–1) for each species and the Einstein A and B coefficients for 1231 (ortho) and 1229 (para) radiative transitions between the levels. The collisional rate coefficients, required for the analysis, are calculated with the help of a scaling law. Very exciting results are obtained; we have analyzed 6 potential transitions for each species of CH2(CN)2, which may play important role in the identification of malononitrile in a cosmic object. DOI: 10.1134/S1063772920090048
1. INTRODUCTION The malononitrile (CH2(CN)2), one of the members of dinitrile group, has been studied in laboratories from time to time [1–6]. It is asymmetric top molecule with C2v symmetry, having electric dipole moment μ = 3.735 D along the b -axis of inertia [1]. Though the malononitrile has large electric dipole moment, its detection in a cosmic object is still awaited. Recently, Motiyenko et al. [6] have studied rotational spectrum of malononitrile and have reported rotational and centrifugal distortion constants in the Ir representation for Watson’s Hamiltonian with the A-reduction, given in Table 1. For obtaining information about some potential spectral lines of malononitrile, which may play important role for its identification in a cosmic object, we have carried out Sobolev large velocity gradient (LVG) analysis. For the LVG analysis, the required input data are the radiative transition probabilities for radiative transitions, and the collisional rate coefficients for collisional transitions between the levels. 1 Dedicated
to Prof. Dr. D.A. Varshalovich, Russia, who left for heavenly abode on April 21, 2020.
Using the spectroscopic data (rotational and centrifugal distortion constants, and electric dipole moment), for each of the species, we have calculated energies of 250 lower rotational levels (up to 98 cm–1
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