A first study of the infrared emission in argon excited by ionizing particles

We report on the study of infrared emission from gaseous argon excited by MeV protons in the wavelength range 0.7-1.8 mun. The dependence of the light yield on the applied electric field has been measured at different pressures. At zero held (prompt emission) the yield does not depend on pressure. When a field is applied the light emission increases linearly with the field strength above a critical value (drift emission) and a dependence from pressure is observed. Prompt and drift emission are consistent with transitions between the lowest atomic states of neutral argon. Drift emission is generated by electrons which gain energy from the electric field and excite atoms through collisions. (C) 2001 Elsevier Science B.V. All rights reserved.