Optical absorption spectra and kinetic behavior of helium excited diatomic molecule (a 3Σu+)

Abstract

The transient absorption spectra of electron-irradiated 12-atm helium have been measured in the wavelength region 3000-11000 Å. The observed molecular absorptions correspond to the c 3Σg+←a 3Σu+, e 3Πg←a 3Σu+, and i 3Πg←a 3Σu+ transitions, short-lived atomic absorptions arising from He*(23S) being observed at several wavelengths. The rotational temperature of He*2(a 3Σu+, v″ = 0) produced initially is estimated to be room temperature from the intensity distribution of the P branch. The vibrational deactivation rate of He*2(a 3Σ u+, v″ = 1) depends linearly on helium pressure, the rate constant being 1.0×10-14 cm3sec-1. The rate constants of the quenching reactions of He*2(a 3Σu+, v″ = 0) by Ne, Ar, Kr, Xe, H2, N2, O2, CO NO, N2O, and CO 2 have been determined from time-dependent measurements of the absorption decay. The rate constants range from 0.4×10-10 cm3sec-1 for Ne to 1.0×10-9 cm 3sec-1 for CO2. An intense emission and absorption were observed at 7772 Å in the quenching processes of He*2(a 3Σu+, v″ = 0) by oxygen-containing compounds. © 1980 American Institute of Physics.