TIME EVOLUTION OF THE POPULATION VERSION BETWEEN (A(3)SIGMA(U)(+), V'') AND (B(3)PI(G), V') STATES IN THE POSITIVE-COLUMN OF A NITROGEN PULSED DISCHARGE

Time transients of population difference between a (3) Sigma(u)(+)(v''=0) and B (3) Pi(g)(v'=2) states were measured in a positive column of moderate-current nitrogen pulsed discharge. The population difference was evaluated from integrated high-resolution laser absorption/gain profiles. Optical gain, due to the population inversion, was present during the first 3-6 mu s of the discharge pulse. The population difference was 0.3 x 10(12) at the peak current of 1 A. Experiments were done at 0.5 Torr pressure and current densities in the range from 0.6-16 a cm(-2). The simple kinetic model, which includes collisions with electrons and molecular nitrogen, and takes into account vibrational excitation of N-2(X), reproduces surprisingly accurately the measured time transients of population difference.