Intersystem crossing pressure dependence

A molecule could also relax from S, or T, to S0 by emitting a photon. The radiational transition Sj —> S0 is called fluorescence (Box 18-2), and the radiational transition T, —> S0 is called phosphorescence. The relative rates of internal conversion, intersystem crossing, fluorescence, and phosphorescence depend on the molecule, the solvent, and conditions such as temperature and pressure. The eneigy of phosphorescence is less than the energy of fluorescence, so phosphorescence comes at longer wavelengths than fluorescence (Figure 18-14). 

Thus the activation volume AV for the rate constant kp of an individual ES reaction pathway can be evaluated if the pressure dependencies of the photoreaction quantum yield, of intersystem crossing and of the ES lifetime can be separately determined. However, such parameterization becomes considerably more complex if several different excited states are involved or if a fraction of the photosubstitution products are formed from states that are not vibrationally relaxed with respect to the medium. Currently, parameterization of pressure effects on photosubstitutions has been attempted for a limited number of metal complexes. These include certain rhodium(III) and chromium(III) amine complexes and some Group VI metal carbonyls, which will be summarized here. 

IV. Pressure Dependence of Collision Induced Intersystem Crossing.329... 

IV. PRESSURE DEPENDENCE OF COLLISION-INDUCED INTERSYSTEM CROSSING... 

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