Measurement of vibrational energy transfer of OH (A2Σ+,v′=1→0) in low-pressure flames

2 Σ⁺) was measured in a low-pressure H₂/O₂ flame for three rotational levels of OH (v^′=1). Rate coefficients for collisions with H₂O and N₂ were determined. At 1600 K, k_VET (N₂) is (in 10^-11 cm³s^-1) 10.1±2, 6.1±1.8, and 3.8±1.3 for N^′=0, 5, and 13, respectively. The k_VET (H₂O) is <1.1±1.8. The k_Q (N₂) is <2.4±8 for both vibrational levels. The k_Q (H₂O) in v^′=1 is 59.1±6.5, 54.7±6.4, and 54.9±6.6 for N^′=0, 5, and 13, respectively, and, determined indirectly, 74.6±10.4, 70.6±10.3, and 63.4±7.3 for N^′=0, 5, and 13 in v^′=0. A multi-level model of OH population dynamics, which is being developed for the quantitative simulation of experimental LIF spectra, was extended to include VET. It was attempted to simulate state-to-state-specific VET coefficients for N₂ collisions. From these simulations it appears that angular momentum conservation does not determine the N dependence of the vibrational relaxation step. Received: 9 September 1996/Revised version: 6 January 1997