Photodissociation of vibrationally excited OH/OD radicals

D.C. Radenovic, A.J.A. Van Roij, S.M. Wu, J. J.Ter Meulen, D.H. Parker, M.P.J. Van Der Loo, L.M.C. Janssen, G.C. Groenenboom

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)

Abstract

This paper describes a joint experimental and theoretical study of the photodissociation of vibrationally excited hydroxyl radicals. OH and OD radicals produced in a pulsed electric discharge supersonic beam are state-selected and focused by a hexapole and then photo-dissociated by a single laser tuned to various H/D or O atom (2 + 1) resonance enhanced multiphoton ionization (REMPI) wavelengths between 243 nm and 200 nm. The angle velocity distributions of the resulting O+ and D+ photofragment ions were recorded using velocity map imaging. Photodissociation to the O(3PJ) + H(2S) limit is shown to take place by one-photon excitation to the repulsive 1 2- state. The experimental data shows that vibrationally excited OH/OD which are formed in the discharge are dissociated, and a vibrational temperature of 2000 K was estimated for the beam source. An analysis in the high-energy recoil sudden limit is used to predict the O(3PJ) fine structure branching ratios and alignment information in the molecular and laboratory velocity frame of the imaging experiment. The measured and predicted fine structure branching ratios and alignment parameters agree well at all dissociation wavelengths, supporting the model for photodissociation in the sudden limit regime. Several aspects of the experiment such as OH pre-alignment and orientation, ion-recoil, and Doppler-free imaging are discussed.

Original languageEnglish
Pages (from-to)557-572
Number of pages16
JournalMolecular Physics
Volume106
Issue number2-4
DOIs
Publication statusPublished - Jan 2008
Externally publishedYes

Keywords

  • Atom polarization
  • Hydroxyl radical
  • Photodissociation
  • State selection
  • Sudden limit model

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