Time-resolved Fourier transform infrared emission spectroscopy of molecular ion

Time-resolved Fourier transform infrared emission spectroscopy in the 1800–4000 cm−1 region has been applied to a kinetic study of a pulsed discharge in He/H2 mixture. Only several low J and K transitions of the ν2 band of H 3 + , together with the atomic lines of neutral helium and hydrogen, were found in the spectrum. The rotational temperature of H 3 + was determined to be 135 ± 37 K. The time-resolved profiles show excitation of helium, followed by formation of excited H 3 + and then of a hydrogen atom. Emission from atomic hydrogen in the n = 5 state appeared in afterglow plasma, implying occurrence of an H 3 + and electron recombination process.