α particle induced scintillation in dense gaseous argon: emission spectra and temporal behavior of its ionic component

The scintillation induced by α particles in dense gaseous argon (above 1 atm) has been studied. The electric field dependence of the scintillation, shows that the second continuum (centred around 1270A) stems from the neutral as well as from the ionic species, initially created by the impinging particle. Intensity decay curves and emission spectra of these neutral excitation and ionic components were determined. Time constants suggest that the recombination mechanism is responsible for a delayed formation of the second continuum states, 1Σ+sub(u) and 3Σ+sub(u). The third continuum of the emission spectra, which spreads at longer wavelengths, from 1600A to 2800A, is field independent