The formation ratio of the two spin-orbit states, 3P0 / 3P2, of the metastable argon, Ar*, was investigated by the glow discharge of a pulsed Ar supersonic beam. The 3P0 / 3P2 ratio decreased with the increase of the glow discharge potential Vg, by which the electron bombardment initiates the discharge. The observed Vg-dependence clearly showed an inverse behavior against Vg as compared with that in the conventional electron impact by low beam densities.

An active control for changing the relative population of the 3P0 fine-state of Ar* in a supersonic beam was investigated in a glow discharge by adding a small amount of foreign gases to pure Ar gas. The Ar* mean velocity was determined to be constant at major positions of the time profile, except for a rise and the decay of the beam for all gas mixtures, and also pure Ar. The relative population of 3P0 decreased with the discharge potential for the addition of ethylene, cyclohexane, and benzene. However, the addition of N2 and CH4 and pure Ar, did not show such a 3P0 decrease. These dissimilar behaviors of the foreign mixed gases could be interpreted based on a difference in the ionization potential of the molecules. A useful application of this population control is discussed.