Infrared luminescence of Xe2 excimers produced by electron impact in dense gas

We observed the infrared emission spectrum of Xe₂ excimers produced by bombarding pure Xe gas and a Ar-Xe mixture with 70 keV electrons. The spectrum is a continuum centered around 7800 cm^-1 of width 900 cm^-1. A Franck-Condon analysis of its shape at low pressure (P=0.1 MPa) has allowed to infer that the emission is due to a bound-free transition between 0_u ⁺ and 0_g ⁺ molecular states correlated with 6p and 6s atomic limit, respectively. The spectrum shows a strong redshift and broadening as pressure is increased up to 3.3 MPa. The shift is explained in terms of dielectric screening and quantum multiple scattering. The different broadening in the pure gas and in the mixture is believed to be a manifestation of the quantum indistinguishability of identical particles.