Excitation and polarization analysis of the OD fragment radiation produced by dissociative electron impact on D2O

Abstract

The formation of electronically excited OD(A2Σ+) radicals following dissociative electron impact on D2O has been studied and a comparison with the H2O/OH (A2Σ+) dissociation system is made. Measurements of excitation functions reveal that the dissociation paths are largely unaffected by the deuteration of the parent molecule and even the weighting of the different dissociation channels leading to respectively slowly and rapidly rotating OD radicals is similar to the H2O dissociation process. On the other hand, the level of polarization of OD as compared with OH fragment radiation is found to be reduced by roughly a factor of 3. This may be explained in terms of an enhanced ratio of lifetime to rotational period for the parent D2O states. Thus the dissociation dynamics, i.e., the time scale between excitation and fragmentation, is demonstrated to react very sensitively when normal water is replaced by its deuterated specimen.