Altitude resolved sprite spectra with 3 ms temporal resolution

Altitude resolved sprite spectra have been obtained with an imaging slit spectrograph with 3 ms temporal and similar to 3 nm spectral resolution. Spectral coverage is from 640 to 820 nm. The slit was vertical to provide altitude resolution. The observed spectra are exclusively composed of emissions from the N-2 first positive (1PG) bands. There are no obvious N-2(+) Meinel emissions, probably due to a combination of quenching and rapid motion of the streamer heads in which ionization is assumed to take place. The spectral analysis shows that the vibrational population in the upper state of the 1PG bands, N-2 B (3)Pi(g) state, varies with altitude and is similar to that of laboratory afterglow at high pressure. This result suggests that secondary interactions among excited states created by electron impact may also play a role in exciting the B (3)Pi(g) state.