Infrared emission spectrum and potentials of 0⁺_uand 0⁺_gstates of Xe₂excimers produced by electron impact

Abstract

We present an investigation of the Xe2 excimer emission spectrum observed in the near infrared range about 7800 cm −1 in pure Xe gas and in an Ar (90%) -Xe (10%) mixture and obtained by exciting the gas with energetic electrons. The Franck-Condon simulation of the spectrum shape suggests that emission stems from a bound-free molecular transition never studied before. The states involved are assigned as the bound (3)0 + u state with 6p [1/2]0 atomic limit and the dissociative (1)0 + g state with 6s [3/2]1 limit. Comparison with the spectrum simulated by using theoretical potentials shows that the dissociative one does not reproduce correctly the spectrum features.

Gaseous and dual-phase time projection chambers for imaging rare processes

“…A strong continuum around 1250 nm in Ar/Xe and Xe mixtures, with yields close to those observed in the VUV region, has been recently reported [144,145]. Technically, IR detection can be accomplished at near 100% quantum efficiency, and the scintillation time constants will be presumably faster than the ones of the VUV precursors [129].…”

Infrared luminescence of Xe<inf>2</inf> excimers produced by electron impact in dense gas

“…The simulation of the spectrum by means of Franck-Condon calulations, shown as a thick solid line in Fig.1, shows that the assignment is correct [34].…”

A battery-operated, stabilized, high-energy pulsed electron gun for the production of rare gas excimers

“…Our experiment on IR luminescence of rare gas excimers 12,13 requires that the charge injection into the gas is pulsed whereas the current emitted from the filament is continuous. In order to achieve a pulsed charge injection, we have introduced a magnetic coil wound around a core of grain-oriented steel laminations (sm in Figure 1) that is powered by a homemade power supply that can be operated at a frequency up to 1 kHz.…”

“…The spectral investigation of such IR luminescence, also as a function of the gas density, has allowed us to assign the molecular states involved in the transition and to elucidate the nature of the interaction of the excimer with its environment. 12,13 The same physical process is at the base of the working principle of the Xe-based ionizing radiation detectors for high-energy physics, 14 with the only difference that in this case the 172 nm ultraviolet (UV) photon, whose detection tags the passage of the ionizing particle, is detected when the molecules spontaneously decays from the first excited state to the ground state. 15 In our experiment, high-energy electrons were produced in a homemade electron gun in a diode configuration.…”

“…These higher lying molecular states give origin to an infrared (IR) luminescence upon transitions to lower lying states in the energy degradation pathway that eventually leads to the dissociation of the Xe 2 molecule. The spectral investigation of such IR luminescence, also as a function of the gas density, has allowed the researchers to assign the molecular states involved in the transition and to elucidate the nature of the interaction of the excimer with its environment 8,9 .…”