NH A 3Πi quenching at 1400 K

Abstract

We have measured electronic quenching rate constants, kQ, in the NH A 3Πi, v′=0 state for several quencher molecules at 1400 K. The NH radicals were produced in a laser pyrolysis apparatus when a mixture of SF6, CF4, NH3, and added quencher was irradiated by a CO2 laser. The ground state NH radicals were then excited to the A state by a pulsed tunable dye laser. The fluorescence decay rates as a function of added quencher pressure yielded the rate constants. The thermally averaged cross sections, σQ=kQ/〈v〉, for NH at 1400 K are all smaller than those observed for OH at 1200 K in this laboratory. In most cases, our high temperature σQ’s are the same as those observed elsewhere at room temperature. These experimental σQ’s are all less than those calculated with an attractive forces ‘‘collision complex’’ model.