Abstract

Rate constants for total and state-specific rotational energy transfer (RET) of OH A ²Σ⁺ (v′ = 2) have been measured directly in atmospheric methane–air and methane–oxygen flames for the first time to our knowledge. We used a picosecond Raman-excimer laser (τ_l = 300 ps, λ = 268 nm) to excite the P₁₁(12.5) and Q₁₁(16.5) A –X transitions in the (2, 0) band of OH molecules. We analyzed the resultant fluorescence with a high-resolution spectrometer in combination with a fast-gated, intensified CCD camera (τ_g = 400 ps). We recorded the temporal evolution of the emission spectrum by shifting the detection time with respect to the laser pulse. Measured emission spectra were inverted to yield the time-dependent population of rotational levels in the excited state. We calculated rate constants for RET from the results of the fit. The total RET in v′ = 2 is similar to v′ = 0, 1. The state-specific rates are represented well by a simple energy-gap law.

© 1997 Optical Society of America

Picosecond planar laser-induced fluorescence measurements of OH A² Σ⁺ (ν′ = 2) lifetime and energy transfer in atmospheric pressure flames

Frank C. Bormann, Tim Nielsen, Michael Burrows, and Peter Andresen
Appl. Opt. 36(24) 6129-6140 (1997)

Picosecond investigation of the collisional deactivation of OH A²Σ⁺(v′ = 1, N′ = 4, 12) in an atmospheric-pressure flame

Paul Beaud, Peter P. Radi, Dieter Franzke, Hans-Martin Frey, Bernhard Mischler, Alexios-Paul Tzannis, and Thomas Gerber
Appl. Opt. 37(15) 3354-3367 (1998)

Energy transfer processes in CH A²Δ and B²Σ⁻ in an atmospheric pressure flame

Nancy L. Garland and David R. Crosley
Appl. Opt. 24(23) 4229-4237 (1985)

Thermally assisted fluorescence of laser-excited OH A²Σ⁺ as a flame diagnostic tool

A. A. Neuber, J. Janicka, and E. P. Hassel
Appl. Opt. 35(21) 4033-4040 (1996)

Vibrational energy transfer in laser-excited A²∑⁺ OH as a flame thermometer

David R. Crosley and Gregory P. Smith
Appl. Opt. 19(4) 517-520 (1980)