Fluorescence-detected Raman-optical double-resonance spectroscopy of glyoxal vapor

B. Duval, D. A. King, R. Haines, N. R. Isenor, B. J. Orr*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

A novel Raman-optical double-resonance (ODR) technique is described in detail and applied to studies of molecular glyoxal (C2H2O2). The technique employs a pulsed excitation sequence, consisting of coherent Raman pumping of a molecular rovibrational transition followed by rovibronic probing through visible laser-induced fluorescence (LIF). The experiments demonstrate a 103-fold enhancement of sensitivity, relative to established coherent Raman spectroscopic methods, and enable individual sets of O-, P-, Q-, R-, and S-branch Raman transitions to be distinguished with high specificity under effectively collision-free conditions. For trans_-glyoxal, a typical excitation sequence is X, v = 0, (J", K") X, V2 = 1, (J”, K”) Ã, ' = 0, (J', K'), where X and Ä denote the ground l Ag) and first excited (VA) electronic singlet states, respectively, and v% is the symmetric CO stretching mode of vibration. There is also evidence of contributions from hot bands involving sequences in the low-frequency modes, v’ and v12- The Raman-ODR spectra are analyzed to yield new spectroscopic constants for the X, V2 = 1 vibronic level of trans-glyoxal. Variation of the time delay between Raman-excitation and LIF-probe pulses has permitted direct observation of collision-induced rotational relaxation in the ground electronic manifold of glyoxal at a rate that is ˜6.5 times gas-kinetic.

Original languageEnglish
Pages (from-to)1570-1581
Number of pages12
JournalJournal of the Optical Society of America B: Optical Physics
Volume2
Issue number9
DOIs
Publication statusPublished - 1985
Externally publishedYes

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