State to State Photodissociation Dynamics of Vibrationally Excited D₂O in B Band

The state-to-state photodissociassion dynamics for the B band of D₂O have been explored from quantum dynamical calculations including the electronic ~X and ~B states. The calculations were carried out using a Chebyshev real wave packet method. The calculated absorption spectra, product state distributions, and branching ratios from different initial vibrational states show di?erent dynamic features, due to the different shapes of the vibrational wavefunctions. The initial bending mode (0,1,0) generates two lobes with a shallow minimum on the absorption spectrum and a slight inverted vibrational population of OD(~X )product at high total energies. The rotational state distributions of OD(~X , v=0) product are highly inverted and depend weakly on the initial state and total energy. On the other hand, the ro-vibrational distributions of OD(A~) product strongly oscillate with the total energy, which are dominated by the long-living resonances and depend sensitively on the potential surfaces. The antisymmetric stretching mode (0,0,1) has large OD( ~ A)/OD(~X ) branching ratios at high total energies, which indicates that the B band dissociation proceeds mainly via the adiabatic pathway in some cases.