Deactivation of N2 (A3Σu+, v=0–7) by ground state nitrogen, ethane, and ethylene measured by kinetic absorption spectroscopy

Abstract

Following the excitation of nitrogen and nitrogen/additive mixtures by single electron pulses the metastable nitrogen $A^3{\Sigma }_u^{+}$ is detected in its vibrational levels v=0–7 by absorption spectroscopy. The additives are ethylene, ethane, and NO. In pure nitrogen the prevailing process is a vibration‐vibration (V‐V) energy transfer process of the N₂ A, v≥2 with Δv=2 to groundstate nitrogen. The rate constants increase with higher quantum numbers i.e., improving energy resonance up to a limiting collisional efficiency for this process of 10⁻². The kinetic behavior of the vibrational states v=5, 6, 7 indicates strongly a collision induced intersystem crossing with the ${\mathrm{N}}_2{B}^3{\Pi }_g$ state. The rate constants for quenching of N₂ A by ethane exhibit a strong increase with rising vibrational quantum number. Ethylene is generally more reactive and shows no strong dependence on the vibrational level. This is interpreted as a fast quenching of the electronic state by ethylene. While this latter process is relatively slow with ethane there exists a fast relaxation of the higher vibrational states by V‐V energy transfer with Δv=1. The deactivation of N₂ A, v=0, 1 by NO is investigated because of the importance of this process as indicator for N₂ A. The rate constants for the two levels are found to be ${\text{(2.8± 0.5)× 10}}^{\text{−11}}$ and ${\text{(6.6± 1.2)× 10}}^{\text{−11}}{\mathrm{cm}}^3/\sec$ , respectively.