Photodissociation of water induced by a long UV pulse and probed by high energy resolution x ray absorption spectroscopy

A UV pump x ray probe UVX PP experiment for probing UV initiated dissociation of the water molecule with long pulses is proposed on the basis of theoretical simulations. With long overlapping UV and x ray pulses, we can obtain high spectral resolution x ray absorption or ionization spectra, containing detailed information about dynamics in the intermediate valence excited state. The dynamics can be influenced with frequency detuning of the pump UV pulse, which acts as a camera shutter by regulating the duration of the UVX PP process. Thereby, this UVX PP setup gives access to ultrafast dynamics of the nuclear wave packet without experimentally challenging requirements of ultrashort pulses and controlled delay times. In a case study of the water molecule, we focus on the lowest UVX PP channel 1b1 amp; 8594;4a1, 1a1 amp; 8594;1b1 where both intermediate valence excited and final core excited states are dissociative. The variation of the UVX PP duration, controlled by the UV detuning, and different dispersion laws of so called molecular and atomic bands allow one to study the dynamics of fragmentation of the water molecule in the intermediate state. A feature is that the long lifetime of intermediate valence excited states opens a door for studies of photoinduced dissociation of polyatomic molecules with heavy fragment