First Comprehensive Analysis of the A-X IR Spectrum of $I_{2}$: An Application of the Near-Dissociation Theory

Abstract

A high resolution absorption spectra of the $A^{3}\Pi_{1u}-X^{1}\Sigma^{+}_{g}$ system of $I_{2}$, consisting of approximately 9700 lines of some 79 bands spanning the vibrational range $v^{\prime} = 0 - 35$ and $v^{\prime\prime} = 3 - 17$, has been recorded and analyzed. A fit to them which uses the previously determined accurate molecular constante for the X-state, yields an accurate new set of molecular constants for the A-state, including the A-doubling constants. The A-state vibrational and inertial rotational constants, as well as mechanically consistent centrifugal distortion constants were represented by near-dissociation expansions. Perturbations due to crossings of level of the $A^{\prime}$-state are observed and assigned.