Efficiencies of state and velocity-changing collisions of superthermal CN A(2)Pi with He, Ar, N(2) and O(2)

Phys Chem Chem Phys. 2007 Feb 14;9(6):747-54. doi: 10.1039/b614965k. Epub 2006 Dec 18.

Abstract

Polarized laser photolysis of ICN is combined with saturated optical pumping to prepare state-selected CN Alpha(2)Pi (nu' = 4, J = 0.5, F(2), f) with a well-defined anisotropic superthermal speed distribution. The collisional evolution of the prepared state is observed by Doppler-resolved Frequency Modulated (FM) spectroscopy via stimulated emission on the CN Alpha(2)Pi-Chi(2)Sigma(+) (4,2) band. The phenomenological rate constants for removal of the prepared state in collisions with He, Ar, N(2) and O(2) are reported. The observed collision cross-sections are consistent with attractive forces contributing significantly for all the colliders with the exception of He. The collisional evolution of the prepared velocity distribution demonstrates that no significant back-transfer into the prepared level occurs, and that any elastic scattering is strongly in the forward hemisphere.

MeSH terms

  • Argon / chemistry*
  • Cyanides / chemistry*
  • Free Radicals / chemistry
  • Helium / chemistry*
  • Nitrogen / chemistry*
  • Oxygen / chemistry*
  • Quantum Theory*
  • Sensitivity and Specificity
  • Spectrophotometry / methods
  • Time Factors

Substances

  • Cyanides
  • Free Radicals
  • Helium
  • Argon
  • Nitrogen
  • Oxygen