Theoretical investigation of the relaxation of the bending mode of CH₂(X̃) by collisions with helium

Lifang Ma; Paul J Dagdigian; Millard H Alexander

doi:10.1063/1.4902004

Theoretical investigation of the relaxation of the bending mode of CH₂(X̃) by collisions with helium

J Chem Phys. 2014 Dec 7;141(21):214305. doi: 10.1063/1.4902004.

Authors

Lifang Ma¹, Paul J Dagdigian², Millard H Alexander³

Affiliations

¹ Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA.
² Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218-2685, USA.
³ Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2021, USA.

PMID: 25481142
DOI: 10.1063/1.4902004

Abstract

We have earlier determined the dependence on the bending angle of the interaction of the methylene radical (CH2) in its X̃³B₁ state with He [L. Ma, P. J. Dagdigian, and M. H. Alexander, J. Chem. Phys. 136, 224306 (2012)]. By integration over products of the bending vibrational wave function, in a quantum close-coupled treatment we have calculated cross sections for the ro-vibrational relaxation of CH 2(X̃). Specifically, we find that cross sections for a loss of one vibrational quantum (v(b) = 2 → 1 and 1 → 0) are roughly two orders of magnitude smaller, and those for a loss of two vibrational quanta (v(b) = 2 → 0) four orders of magnitude smaller, than those for pure rotational relaxation. In addition, no clear cut dependence on the energy gap is seen.