ROTATIONAL STRUCTURE OF VIBRONIC ABSORPTION AND LUMINESCENCE SPECTRA OF NO-2 IMPURITY MOLECULES IN POTASSIUM HALIDE CRYSTALS

The rotational structure of the pure‐electronic (near 4000 Å) and other zero‐phonon lines associated with v1 and v2 modes is observed in the vibronic spectra of NO −2 ions in KCl and KBr crystals at liquid helium temperature. Three components in the (0, 0) group of the absorption spectrum of KCl‐NO −2 have the intervals 7 and 10 cm−1, the resonant (0, 0) group in emission consists of two components. In the KBr host some components show additional splitting. The rotation of NO −2 in KCl about the top axis a is found to be somewhat hindered in the ground state and nearly free in the excited electronic state. Some emission occurs from thermal nonequilibrium rotational states which gives evidence for rather slow rotation‐phonon relaxation. Several groups of the absorption spectra exhibit rotational perturbations which are suggested to be caused by Coriolis interaction between the vibrations v′1(A1) and v′3(B1). Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim