TY - JOUR
T1 - Frequency modulated spectroscopy as a probe of molecular collision dynamics
AU - Alagappan, Azhagammai
AU - Costen, Matthew L.
AU - McKendrick, Kenneth G.
PY - 2006/4
Y1 - 2006/4
N2 - We describe the application of frequency modulated spectroscopy (FMS) with an external cavity tuneable diode laser to the study of the scalar and vector properties of inelastic collisions. CN X2S+ radicals are produced by polarized photodissociation of ICN at 266 nm, with a sharp velocity and rotational angular momentum distribution. The collisional evolution of the distribution is observed via sub-Doppler FMS on the A 2?-X2S+ (2,0) band. He, Ar, N 2, O2 and CO2 were studied as collider gases. Doppler profiles were acquired in different experimental geometries of photolysis and probe laser propagation and polarization, and on different spectroscopic branches. These were combined to give composite Doppler profiles from which the speed distributions and specific speed-dependent vector correlations could be determined. The angular scattering dynamics with species other than He are found to be very similar, dominated by backward scattering which accompanies transfer of energy between rotation and translation. The kinematics of collisions with He are not conducive to the determination of differential scattering and angular momentum polarization correlations. Angular momentum correlations show interesting differences between reactive and non-reactive colliders. We propose that this reflects differences in the potential energy surfaces, in particular, the nature and depth of attractive potential wells. © 2005 Elsevier B.V. All right reserved.
AB - We describe the application of frequency modulated spectroscopy (FMS) with an external cavity tuneable diode laser to the study of the scalar and vector properties of inelastic collisions. CN X2S+ radicals are produced by polarized photodissociation of ICN at 266 nm, with a sharp velocity and rotational angular momentum distribution. The collisional evolution of the distribution is observed via sub-Doppler FMS on the A 2?-X2S+ (2,0) band. He, Ar, N 2, O2 and CO2 were studied as collider gases. Doppler profiles were acquired in different experimental geometries of photolysis and probe laser propagation and polarization, and on different spectroscopic branches. These were combined to give composite Doppler profiles from which the speed distributions and specific speed-dependent vector correlations could be determined. The angular scattering dynamics with species other than He are found to be very similar, dominated by backward scattering which accompanies transfer of energy between rotation and translation. The kinematics of collisions with He are not conducive to the determination of differential scattering and angular momentum polarization correlations. Angular momentum correlations show interesting differences between reactive and non-reactive colliders. We propose that this reflects differences in the potential energy surfaces, in particular, the nature and depth of attractive potential wells. © 2005 Elsevier B.V. All right reserved.
KW - Angular momentum polarization
KW - Diode laser
KW - Doppler spectroscopy
KW - Inelastic scattering
UR - http://www.scopus.com/inward/record.url?scp=33644925812&partnerID=8YFLogxK
U2 - 10.1016/j.saa.2005.10.050
DO - 10.1016/j.saa.2005.10.050
M3 - Article
C2 - 16495130
SN - 1386-1425
VL - 63
SP - 910
EP - 922
JO - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
JF - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
IS - 5
ER -