Frequency modulated spectroscopy as a probe of molecular collision dynamics

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)910-922
Number of pages13
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Issue number5
Publication statusPublished - Apr 2006


  • Angular momentum polarization
  • Diode laser
  • Doppler spectroscopy
  • Inelastic scattering


Dive into the research topics of 'Frequency modulated spectroscopy as a probe of molecular collision dynamics'. Together they form a unique fingerprint.

Cite this