Probing Molecular Dynamics with Laser Photoelectron Spectroscopy
Nonradiative relaxation processes such as internal conversion and intersystem crossing have been of interest to photochemists for a number of years. Although the decay of an initially prepared state can be studied by monitoring fluorescence lifetimes or quantum yields, observation of the state that is populated by the radiationless transition is usually difficult. In principal, this can be accomplished by absorption experiments, but in practice such signals are usually weak. In recent years the method of multiphoton ionization spectroscopy has grown in popularity.1–3 It has often been pointed out that one of the advantages of this technique is that it can be used to detect “dark” or non-fluorescing excited states such as those populated during radiationless relaxation. Smalley, Johnson and coworkers4,5 have shown that triplet states of benzene populated following intersystem crossing from the initially excited B2U state are ionizable and that kinetic information about the triplet state populated can be measured.
KeywordsTriplet State Photoelectron Spectrum Vibrational Excitation Kinetic Energy Distribution Electron Kinetic Energy
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