The dispersed fluorescence spectrum of NaAr: Ground and excited state potential curves

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Abstract
The van der Waals molecule NaAr has been prepared by supersonic free jet expansion of a mixture of sodium, argon, and helium. The A 2Π←X 2Σ+ electronic transition has been excited by a tunable dye laser and the resulting A→X fluorescence has been studied. The dispersed fluorescence spectra display both discrete and diffuse features, corresponding to transitions from excited vibrational levels of the A state to bound and unbound levels of the X state. The characteristic reflection structure in the bound‐free spectra permits an unambiguous assignment of the vibrational numbering in the A state. This assignment and the previously measured spectroscopic constants are used to calculate the potential curve of the A state. The discrete structure in the fluorescence spectra is analyzed and, together with the previous measurements, is used to determine the potential curve of the X state in the well region. The repulsive part of the X curve is then deduced through trial‐and‐error simulation of the biund‐free spectra. The potential curves derived in this work are compared critically with results of several previous experimental and theoretical studies of NaAr.