Ab initio quantum mechanical investigation of the photodissociation of HI and DI

The photoabsorption spectra of HI and DI are computed using ab initio potential curves and transition dipole moments. Partial absorption cross-sections and quantum yields for the production of the ground state (2P3/2) and the excited spin–orbit state (2P1/2) of iodine are calculated using the time-dependent wave packet formalism as functions of the excitation energy. Very good overall agreement with experimental data is obtained for the band total absorption spectrum and for the I(2P1/2) quantum yield. The spin–rotational coupling of the a3Π0+ and A1Π1 states is estimated for the first time and is shown to play a negligible role in the HI photodissociation.