Excitation transfer from Ar* to H-2 in a gas-discharge plasma

Spectral distributions of the emission intensity over a range of 200-400 nm , where the dissociation continuum (a(3)Sigma(g)(+) --> b(3)Sigma(u)(+)) of a hydrogen molecule is located, are measured in a hollow-cathode glow-disc harge plasma of mixtures of hydrogen with argon, neon, and krypton at press ures of 0.8 to 10 torr. The continuum shape is found to be substantially de pendent on the ratio of constituents of the Ar-H-2 mixture. Within the limi ts of experimental accuracy, the shape of the continuum of a mixture of hyd rogen with neon and krypton is the same as that of pure hydrogen. The exper iments carried out with the active phase and afterglow of the discharge dem onstrated that a change in the continuum shape in the presence of argon res ults from the excitation transfer from long-lived excited states of argon a toms to H-2 molecules. Possible excitation transfer mechanisms are analyzed . It is shown that, if energy considerations are used, the rotational and t ranslational energies of an H-2 molecule should be taken into account.