Coupled-channel study of rotational excitation of a rigid asymmetric top by atom impact: (H/sub 2/CO,He) at interstellar temperatures. [cross section convergence, quantum mechanics, pumping model, resonance, Maxwell--Boltzmann distribution, statistical, equilibrium]
A quantum mechanical scattering study is carried out to test a collisional pumping model for cooling the 6 and 2 cm doublets of interstellar formaldehyde. The Arthurs and Dalgarno formalism is extended to the collision of an s-state atom with a rigid asymmetric top molecule and applied to rotational excitation of ortho formaldehyde by helium impact. Using a previously determined configuration interaction potential energy surface, the coupled-channel (CC) equations are integrated at 12 scattering energies between 20 and 95degreeK. Up to 16 ortho formaldehyde states, yielding a maximum of 62 CC equations, are retained to test convergence of computed cross sections. Resonance structure is obtained at approx.20.2, 32.7, and 47.7degreeK. The computed inelastic cross sections are averaged over a Maxwell--Boltzmann distribution and the resultant rates used to solve the equations of statistical equilibrium for the relative populations. The 6 and 2 cm doublets are found to be cooled only upon inclusion of the j=3 doublet. (AIP)
- Research Organization:
- Department of Chemistry and Inorganic Materials Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
- OSTI ID:
- 7342779
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 65:6; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALDEHYDES
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
COLLISIONS
CRYOGENIC FLUIDS
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FLUIDS
FORMALDEHYDE
HELIUM
INTERSTELLAR SPACE
MOLECULE COLLISIONS
NONMETALS
ORGANIC COMPOUNDS
RARE GASES
ROTATIONAL STATES
SPACE