Luminescence spectra of nitrogen in solid argon I. Experiment

The X‐ray stimulated luminescence spectra of Ar crystals having 0.01% and 5% N 2 impurities were studied at 4.2 and 77 K, in the region of the Vegard‐Kaplan (A 3 Σ → X 1 ΣΣ ) bands. Each band of the 5% N 2 /Ar system, at 4.2 K, was composed of three, almost equispaced, peaks. The fine structure was defined by a two‐peak asymmetric sideband, between 25 and 180 cm −1 , to the red of the N 2 electronic‐vibrational transition. At other impurity concentrations and crystal temperatures, different relaxation rates were found but no fine structure was observed. The whole Vegard‐Kaplan band system for N 2 /Ar at 4.2 K was found to be shifted by (128 ± 15) cm −1 , to the red of V 00 ,. the free molecule transition.