Vibrational energy transfer in laser-excited A(2)Sigma(+) OH as a flame thermometer

Abstract

OH molecules in the burnt gases of a methane-air flame are excited to individual rotational levels of the v' = 0 level of the. A(2)Sigma(+) state using a tunable pulsed laser. Some of the laser-excited molecules undergo upward collisional energy transfer to v' = 1 before radiating. A measurement of the ratio of the populations in these two vibrational levels, together with an estimate of the relative rates of vibrational transfer and quenching and the invocation of detailed balancing, furnishes the temperature of the flame. The method should be suitable for the single-pulse simultaneous measurement of the temperature and the concentration of OH, a reactive intermediate species.