Kinetic study of ground state atomic nitrogen, N(24S), by time-resolved atomic resonance fluorescence

Abstract

Ground state nitrogen atoms, N(2⁴S), generated by pulsed photochemical initiation, have been, studied by time-resolved resonance fluorescence following optical excitation in the vacuum ultraviolet, λ= 120 nm, N[2p,²3s(⁴P_{½,,[graphic omitted]})→ 2p³(⁴S)]. Atomic nitrogen, principally in the optically metastable doublet states, N[2p³(²D_J, ²P_J)], was produced by the repetitive vacuum ultraviolet photolysis of N₂O and collisionally quenched to the ⁴S state by the use of N₂ as a buffer gas. Photoelectric detection of the vacuum u.v. signals employed photon counting coupled with signal summation in a multiscalar. Considerable care was required to eliminate spurious photon signals at λ= 130 nm due to O(2³P_J)[O(3³S₁)→ O(2³P_J)]. Absolute rate data for the collisional removal of N(2⁴S) in the presence of the gases NO, NO₂, O₃ and C₂H₄ are presented and compared with previously reported data. The results for N + C₂H₄ are further discussed in relation to the “HCN limiting yield” method that has been employed hitherto as a marker for N atom kinetics.