Rotational state specific dissociation dynamics of D2O via the (C)over-tilde(010) state: The effect of bending vibrational excitation

The rotational state resolved photodissociation dynamics of D2O via the (C) over tilde (010) state has been investigated by using the D-atom Rydberg tagging time-of-flight technique combined with a tunable vacuum ultraviolet light source. The D-atom action spectrum of the (C) over tilde (010) <- (X) over tilde (000) band and the corresponding time-of-flight (TOF) spectra of D-atom photoproducts formed following the excitation of D2O to individual rotational transition have been measured. By comparison with the action spectrum of the (C) over tilde (000) <- (X) over tilde (000) band, the bending vibrational constant of the (C) over tilde state for D2O can be determined to be v(2) = 1041.37 +/- 0.71 cm(-1). From the TOF spectra, the product kinetic energy spectra, the vibrational state distributions of OD products, and the state resolved anisotropy parameters have been determined. The experimental results indicate a dramatic variation in the OD product state distributions for different rotational excitations. This illuminates that there are two distinctive coupling channels from the (C) over tilde (010) state to the low-lying electronic states: the homogeneous electronic coupling to the (A) over tilde B-1(1) state, resulting in vibrationally hot OD(X) products, and the Coriolis-type coupling to the (B) over tilde (1)A(1) state, producing vibrationally cold but rotationally hot OD(X) and OD(A) products. Furthermore, the three-body dissociation channel is confirmed, which is attributed to the (C) over tilde -> (1)A(2) or (C) over tilde -> (A) over tilde pathway. In comparison with the previous results of D2O photolysis via the (C) over tilde (000) state, it is found that the v(2) vibration of the parent molecule enhances both the vibrational and rotational excitations of OD products.

Automated summary

The photodissociation dynamics of D2O via the (C) over tilde (010) state was studied, showing different product distributions for different rotational excitations.