Survey of the Excited State Dissociation οf Gas-Phase Bromine Monochloride in the Visible-Near UV Wavelength Region

The spectroscopic transitions and photoabsorption/dissociation processes of bromine monochloride (BrCl) via several low-lying covalently bound electronic states and repulsive states have been investigated by performing electronic structure calculations and wave packet simulations of nuclear motion. The absorption spectra for 52-electron singlet systems are obtained by employing time-dependent propagation methods or the real-time propagation of the time-dependent Schrödinger equations in the adiabatically exact approximation. Based on the elastic scattering calculations, the results of angular distributions of the products of photodissociation of BrCl molecules are examined on two aspects: (1) the nature of the state that is prepared by excitation from a bound level into a continuum, and (2) under avoided crossing cases, the influences of nonadiabatic coupling processes on the fragmentation process are evaluated by virtue of a semiclassical Landau-Zener model, which treats an avoided crossing between two states of a given nature and evaluates a nonadiabatic effect relevant to the molecule during photodissociation. The model qualitatively reproduces the key aspects of the full processes related to the transfer of dissociating flux between states of 0+ symmetry, indicating that the proposed coupling scheme is generally correct.