Reaction kinetics of the He(2P) and the He2sup(*)(a,v) states in high-density helium

Helium at pressures ranging from 0.5 to 8 bar was excited by an intense e-beam. The absolute population densities of the He(2 1P), He(2 3P) and He2*(a, v), v = 0, 1, 2 states were determined by measuring the transient absorption of probe light delivered by a dye laser. The experimental data are readily described by a kinetic model taking into account the excitation and de-excitation processes. The recombination of He2+ by a termolecular reaction with e + He to He(2 3P) was determined quantitatively and the rate constants for the termolecular reactions of He(2 1P) and He(2 3P) were evaluated. The rotational and vibrational relaxation of He2(a) by helium was also investigated. (author)