Low-Temperature Emission Spectrum of O2— in Alkali Halides

Abstract

The fluorescence emission spectrum of the O₂^— molecule‐ion has been measured at 4.2°K in the alkali halides NaF, NaCl, NaBr, KCl, RbCl, KBr, RbBr, and KI. The most intense peaks in the emission spectra are shown to be due to transitions to vibrationally excited levels of the ground state of O₂^—. The vibrational properties of O₂^— in its ground state can be represented by an anharmonic oscillator with a vibrational constant (ω_e) of approximately 1170 cm^—1, and an anharmonicity (ω_ex_e) of 8.5 cm^—1. The cause of the fine structure which appears around these intense peaks is not known, but the fine structure for the alkali halides NaF, KCl, and RbBr, which have almost equal anion and cation masses, is quite different from the other alkali halides NaCl, NaBr, KBr, and KI.