Infrared electron relaxation, deactivation

Ten years ago, femtosecond IR spectroscopy of an excess electron in pure water showed the existence of an ultrashort-hved prehydrated state (61). This IR nonequihbrium electronic configuration is built up in less than 120 fs in H2O and represents a direct precursor of the hydrated electron ground state (equation 6). In the infrared (0.99 eV), the monoexponential relaxation of the signal toward an s-hke ground state of the hydrated electron (240 20 fs) has been analyzed in the framework of a two-state model (61, 65). With a similar model, an indirect estimate of the infrared electron relaxation in the red spectral region gives a deactivation rate of 2 X 10 s (62, 66). The very fast appearance of the infrared electron (efn) is comparable to any nuclear motion, solvent dipole orientation, or thermal motion of water molecules. The relaxation of... 

Electronic relaxation in different excited vibronic levels corresponding to the same electronic configuration can be experimentally studied, provided that, as mentioned above, (1) single vibrational levels within the initial electronic state are populated and (2) the excited molecule decays nonradiatively on a timescale much shorter than the mean time between deactivating collisions or by other means such as infrared fluorescence [115]. For typical polyatomic molecules in the gas phase, a narrow-band optical excitation pulse (as small as 1 and shorter relative to the genuine decay times wiH result in the selection of a single vibronic state. U nder these conditions,... 

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