Attenuation of vacuum ultraviolet light in pure and xenon-doped liquid argon - an approach to an assignment of the near-infrared emission from the mixture

TL;DR

This study measures how vacuum ultraviolet light is absorbed in pure and xenon-doped liquid argon, revealing a very long attenuation length in pure argon and identifying xenon-related absorption features that help explain near-infrared emissions.

Contribution

It provides the first lower limit for the attenuation length of scintillation light in pure liquid argon and links xenon absorption features to near-infrared emission in argon-xenon mixtures.

Findings

Pure liquid argon shows no attenuation down to 118 nm.

Attenuation length of pure liquid argon is at least 1.10 meters.

Xenon doping introduces absorption features linked to near-infrared emission.

Abstract

Results of transmission experiments of vacuum ultraviolet light through a 11.6 cm long cell filled with pure and xenon-doped liquid argon are described. Pure liquid argon shows no attenuation down to the experimental short-wavelength cut-off at 118nm. Based on a conservative approach, a lower limit of 1.10 m for the attenuation length of its own scintillation light could be derived. Adding xenon to liquid argon at concentrations on the order of parts per million leads to strong xenon-related absorption features which are used for a tentative assignment of the recently found near-infrared emission observed in electron-beam excited liquid argon-xenon mixtures. Two of the three absorption features can be explained by perturbed xenon transitions and the third one by a trapped exciton (Wannier-Mott) impurity state. A calibration curve connecting the equivalent width of the absorption line at 140 nm with xenon concentration is provided.