Ultrafast Photochemistry in Solutions:
The Mechanisms of Photoionization and Threshold Photodetachment

Fundamental photochemical mechanisms in solution can best be interrogated via small molecule systems where clear comparisons with theory are possible. However, small molecules usually require excitation below 300 nm and their reactions, along with the coupled solvents motions, are faster than 100 femtoseconds. This talk will describe the recent application of a sub-50 fs tunable UV source to address such a fundamental photochemical reaction - electron ejection. The detailed dynamics of threshold photodetachment of aqueous anions are mapped by UV-pump/broadband-probe transient absorption spectroscopy and compared with the two-photon ionization of pure solvent.