Collisional excitation of vinylidene (H2CC)

• Published in: Advances in space research 2014-11, Vol.54 (9), p.1963-1971
• Main Authors: Sharma, M.K., Sharma, Monika, Verma, U.P., Chandra, Suresh
• Format: Article
• Language: English
• Subjects: Collisional rate coefficients; Computer programs; Energy use; Gaussian; H2CC molecule; ISM: molecules; Mathematical analysis; Mathematical models; Maxwellian distribution; Radiative transfer; Rotational
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/j.asr.2014.07.025

Though H2CO, H2CS, H2CCC, H2CCCC, H2CCO have been identified in cool interstellar molecular clouds, identification of H2CC is still awaited. To analyze its spectrum, collisional rate coefficients are required. We have calculated collisional rate coefficients for rotational transitions between 23 levels of ortho and para H2CC for kinetic temperatures 10, 20, 30, 40, and 50K. The scattering problem is analyzed using the computer code MOLSCAT where the colliding partner is He atom. The interaction between H2CC and He has been calculated with GAUSSIAN 2003. For the interaction potential obtained with GAUSSIAN 2003, MOLSCAT is used to derive the parameters q(L,M,M′|E) as a function of energy E of the colliding partner. After averaging the parameters q(L,M,M′|E) over a Maxwellian distribution, the parameters Q(L,M,M′|T) as a function of the kinetic temperature T in the cloud are obtained. Finally, the collisional rate coefficients have been calculated. We have also calculated radiative transition probabilities for the transitions between the rotational levels. Finally, for ortho-H2CC, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer and found that the H2CC may be identified through anomalous absorption of its transition 111–110 at 4.89GHz.