Variation of Radiative Lifetimes of NH2(Ã2A1) with Rotational Levels in the (0,8,0) and (0,9,0) Vibration Bands

Abstract

Radiative lifetimes from the first electronically excited state of the amidogen free radical, NH2(Ã2A1), are reported for rotational states in selected vibrational levels ν2� using laser-induced fluorescence. Thermal collision of argon, Ar*(3P0, 3P2) metastable atoms in a microwave discharge- flow system with ammonia (NH3) molecules produced ground state NH2(X ̃2B1). The radiative lifetimes for the deactivation of NH2(Ã2A1) were determined by measuring the decay profiles of NH2 (Ã2 A1 → X ̃ 2 B1 ). In addition to the Fermi resonances with the ground state that lengthen the ra- diative lifetimes, a systematic increase in the radiative lifetimes with rotational quantum number was observed. Furthermore, the average radiative lifetimes of the (0, 9, 0) 􏰀, τ1 = 18.65 ± 0.47 μs and (0, 8, 0) 􏰁, τ2 = 23.72 ± 0.65 μs levels were much longer than those of the (0, 9, 0) 􏰂, τ3 = 10.62 ± 0.47 μs, and (0, 8, 0) 􏰃, τ 4 = 13.55 ± 0.55 μs states suggesting increased mixing of the first elec- tronic excited and the ground states. © 2012 American Institute of Physics.[doi:10.1063/1.3676782]