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(4P½,,[graphic omitted])→ 2p3(4S)]. Atomic nitrogen, principally in the optically metastable doublet states, N[2p3(2DJ, 2PJ)], 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(23PJ)[O(33S1)→ O(23PJ)]. 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.