Coupled-channel study of rotational excitation of a rigid asymmetric top by atom impact: (H2CO,He) at interstellar temperatures

Barbara J. Garrison, William A. Lester, William H. Miller

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

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 95°K. 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 ∼20.2, 32.7, and 47.7°K. 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.

Original languageEnglish (US)
Pages (from-to)2193-2200
Number of pages8
JournalThe Journal of chemical physics
Volume65
Issue number6
DOIs
StatePublished - Jan 1 1976

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formaldehyde
Formaldehyde
Atoms
Scattering
excitation
atoms
Helium
Potential energy surfaces
Boltzmann distribution
cross sections
scattering
Temperature
configuration interaction
temperature
pumping
potential energy
helium
inclusions
formalism
Cooling

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Garrison, Barbara J. ; Lester, William A. ; Miller, William H. / Coupled-channel study of rotational excitation of a rigid asymmetric top by atom impact : (H2CO,He) at interstellar temperatures. In: The Journal of chemical physics. 1976 ; Vol. 65, No. 6. pp. 2193-2200.
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Coupled-channel study of rotational excitation of a rigid asymmetric top by atom impact : (H2CO,He) at interstellar temperatures. / Garrison, Barbara J.; Lester, William A.; Miller, William H.

In: The Journal of chemical physics, Vol. 65, No. 6, 01.01.1976, p. 2193-2200.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Coupled-channel study of rotational excitation of a rigid asymmetric top by atom impact

T2 - (H2CO,He) at interstellar temperatures

AU - Garrison, Barbara J.

AU - Lester, William A.

AU - Miller, William H.

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N2 - 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 95°K. 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 ∼20.2, 32.7, and 47.7°K. 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.

AB - 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 95°K. 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 ∼20.2, 32.7, and 47.7°K. 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.

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