Photoionization of Vibrationally Excited N2. II. Quenching by CO2 and N2O

Abstract

The rate coefficients for quenching of vibrationally excited N2 in the ground electronic state ( N 2 * ) by CO2 and N2O have been measured using a photoionizationmass spectrometer to detect the N 2 * in a flowing N2 afterglow. The reduction in the photoion count rate at amu 28 when CO2 or N2O is added to the afterglow is obtained at wavelengths longer than the photoionization threshold of ground state N2. The quenching data are analyzed with a kinetic model that includes nearly resonant transfer of vibrational energy from N 2 * to CO2 or N2O followed by radiative, wall, and gas‐phase collisional quenching of the infrared‐active gas. At low N2 partial pressures the measured quenching rate coefficient asymptotically approaches the rate coefficient (k 1) for the V–V transfer reaction. From measurements at wavelengths where N 2 * (v″ =1) is efficiently photoionized, we find that k 1 = 2±1×10−13 and 9±4×10−14 cm3 sec−1 for V–V transfer from N 2 * (v″ =1) to CO2 and N2O, respectively.