Photodissociation Dynamics of H2O via the (E)over-tilde′ (1B2) Electronic State

Photodissociation dynamics of H2O via the (E) over tilde'B-1(2) state were studied using the high-resolution H atom photofragment translational spectroscopy method, in combination with the tunable vacuum ultraviolet free electron laser (VUV FEL). The measured translational energy spectra allow us to determine the respective quantum state population distributions for the nascent OH(X-2 Pi) and OH(A(2)Sigma(+)) photofragments. Analyses of the quantum state population distributions show both the ground and electronically excited OH fragments to be formed with moderate vibrational excitation but with highly rotational excitation. Unlike the dissociation via the lower-lying electronic states, where OH(X) is the major fragment, the OH(A) products are predominant via the (E) over tilde' state. These products are mainly ascribed to a fast dissociation on the (B) over tilde (1)A(1) state surface after nonadiabatic transitions from the initial excited (E) over tilde' state to the (E) over tilde state. Meanwhile, another dissociation pathway from the (E) over tilde' state to the B-1(2) (3)pb(2) state, followed by coupling to the (1)A(2) (3)pb(2) state, is also observed, which yields the OH(X) + H and O(P-3) + 2H products.

Automated summary

In this study, the photodissociation dynamics of H2O via the (E) over tilde'B-1(2) state were investigated using high-resolution H atom photofragment translational spectroscopy method. The analysis of quantum state population distributions revealed that both ground and electronically excited OH fragments exhibit moderate vibrational excitation but high rotational excitation. Additionally, it was found that the OH(A) products are predominantly formed via the (E) over tilde' state.