title: Efficiencies of state and velocity-changing collisions of superthermal CN A(2)Pi with He, Ar, N(2) and O(2).
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.
authors.affiliation: School of Engineering and Physical Sciences, William H Perkin Building, Heriot-Watt University, Edinburgh, UK.
authors.forename: Azhagammai
authors.initials: A
authors.lastname: Alagappan
authors.forename: Iain
authors.initials: I
authors.lastname: Ballingall
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Costen
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: McKendrick
authors.forename: Grant
authors.initials: G
authors.lastname: Paterson
mesh_terms: D001128:Argon / Q000737:chemistry*; D003486:Cyanides / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006371:Helium / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors
chemical_list: D003486:Cyanides; D005609:Free Radicals; D006371:Helium; D001128:Argon; D009584:Nitrogen; D010100:Oxygen