Continua of UV radiation and kinetics of slightly ionized noble gases

Radiation spectra of noble gases at densities from 10 18 to 10 20 cm -3 were investigated for nanosecond e-beam plasmas at approximately 4 A cm -2 current density. New data on the structure of the third UV continuum and on the radiation time scaling were obtained. Experimental data presented in the literature were systematized. Two bands were resolved in the radiation from heavy noble gases which are not bound up with neutral dimers and trimers. A review of the models of origin of the third UV continuum in the radiation spectra of noble gases was carried out. A model is proposed, which attributes the continuum to transitions from low Rydberg states of the molecular ion R 2 + (correlated with R*( 3 P)+R + ( 2 P) states at large internuclear distance) to low repulsive states. The efficiency of energy transfer into the continuum in e-beam plasmas is approximately 2% and is found to agree with experimental data. In a discharge this value might be still higher. The model is used to explain the features of the continuum in He, Ne, Ar and other experimental data.