Calculation of Predissociation Rates of the B 3Π+u State of I2

Abstract

A comparison of the purely radiative decay rates of vibrational levels of the B 3Π0+u state of I2 with total decay rates obtained from several independent lifetime measurements has indicated a significant amount of spontaneous predissociation of the B state. We present here a calculation of the observed relative predissociation rates by means of a model consisting of a repulsive 1u state which is coupled to the υ′J′ levels of the B state by rotational and electronic angular-momentum terms neglected in the zeroth-order Hamiltonian. The heterogeneous predissociation rate between a bound υ′J′ level and a continuum level at the same energy is calculated from Kronig's theory using exact wavefunctions for both levels. The dependence of this rate on the rotational level J′ is taken into account, together with the fractional population of the υ′J′ levels which were excited in the measurement of the total decay rates. Excellent agreement is found between the calculated and observed relative predissociation rates at regions about υ′ of 14, 25, and 50 of the B state for one position of the repulsive state lying very near the repulsive wall of the B state over the energy range 17 300–20 000 cm−1. The position of this state relative to the B 3Π0+u and A 3Π1u states agrees well with Mulliken's prediction of the location of the Π1u1 state of I2.