State-selected reaction and relaxation of NH2[X 2B1(0,ν2,0)] radicals and NO2

Abstract

The reaction of ground and vibrationally excited NH2 (ν″2 =0,1) with NO2 has been studied using the sensitive laser-induced fluorescence (LIF) technique. The state-selected NH2 radical was generated via infrared multiple-photon dissociation (IRMPD) of N2H4, NH3, and CH3NH2. The rate constants obtained at room temperature are kNO2(ν″2 =0)=(2.26±0.08)×10−11 cm3 molecule−1 s−1 and kNO2(ν″2 =1)=(1.73±0.06)×10−11 cm3 molecule−1 s−1. The most prominent feature of the results is the decrease of the reaction rate with vibrational bending mode excitation. A possible reaction mechanism is proposed to account for this observation as well as for previously reported literature values. The vibrational relaxation of NH2(ν″2=1) with CH3NH2 and NH3 have also been studied. The room temperature rate constants are kCH3NH2=(7.4±0.5)×10−11 cm3 molecule−1 s−1 and kNH3=(4.7±0.6)×10−11 cm3 molecule s−1, respectively. A near-resonant vibrational relaxation model is proposed to fit the experimental results.