Measurement of the rate constant for the quenching of I(2P12) by O2(X) at 150 K

Electronic energy transfer between I atoms and O2 molecules, O2(a1Δ) + I(2P12) ↔ O2(X3Σ−) + I(2P12), is a process of central importance in chemical oxygen-iodine laser (COIL) systems. Rate constants for the forward and reverse steps are well defined for room temperature. However, supersonic COIL devices operate with local gas temperatures near 150 K. To facilitate modeling of these lasers, the rate constant for quenching of I(2P12) by O2(X) has been measured at a temperature of 150 K. The result obtained, kb = (4.6 ± 1.0) × 10−12 cm3 s−1, is appreciably smaller than the values used in current computational models.