Comprehensive analysis of the A–X spectrum of I2: An application of near-dissociation theory

High resolution absorption spectra of the A 3Π1u–X 1Σ+g system of I2, consisting of some 9552 lines of some 79 bands spanning the vibrational range v′=0–35 and v″=3–17, have been recorded and analyzed. A fit to them which uses the previously determined accurate molecular constants for the X 1Σ+g state yields an accurate new set of molecular constants for the A state, including the Λ doubling constants. The A-state vibrational and inertial rotational constants, as well as mechanically consistent centrifugal distortion constants, are represented by near-dissociation expansions, yielding an accurate representation of the experimental data which also provides a reliable global representation of all observed and unobserved vibration–rotation levels of this state.