Time-resolved laser-induced fluorescence of atomic nitrogen in a free-burning arc discharge

An experiment to detect ground-state atomic nitrogen in an atmospheric-pressure argon-nitrogen free-burning 200 A arc by time-resolved two-photon laser-induced fluorescence is described. The time decay of the fluorescence pulses showed that quenching of the laser-excited state is rapid. Upper bound estimates of the pulse-decay time were determined as a function of radius, and were found to be on the order of 1 ns, and to decrease with increasing radii. The implications of rapid quenching of the laser-excited state to the application of laser-induced fluorescence as a plasma diagnostic tool are discussed