Exploration for electronic transitions and photodissociation mechanism of hydrogen iodide

The electronic transitions and excited-state fragmentation of hydrogen iodide have been studied within the A-band continuum. The extinction intensity for the excitations from the ground to the low-lying electronic states are derived by performing the wave packet simulations of nuclear dynamics in this study. The quantum yields of the spin-excited I* product at the different photon energies are determined as well. The results suggest that the possibility of intersystem crossing can be neglected. Employing the time-dependent density functional theory (TDDFT), the four highest occupied and the two lowest unoccupied orbitals of hydrogen iodide have been analyzed, and the transition to the state is found to be most probable in the first absorption band.