ULTRAFAST ELECTRONIC RELAXATION DYNAMICS - A COMPARISON BETWEEN WATERAND IONIC AQUEOUS-SOLUTIONS

Femtosecond spectroscopy of aqueous solutions at room temperature allo ws to investigate electronic dynamics triggered by the energy depositi on and a subsequent excess electron photodetachment from solvent or so lute (chloride ion). In ionic aqueous solutions, early physicochemical processes are analyzed within the frequency domain 27 10(3) - 7.7 10( 3) cm(-1) by considering multiple time-resolved electronic relaxation channels: electron localization within the solvation shells of chlorin e atom, electron-ion pair formation, deactivation of excited charge tr ansfer to solvent states (excited CTTS states). At short time (0.5 ps < t < 4ps) ultrafast electron-chlorine atom recombination reaction (k( A) similar to 3 10(12) S-1) competes with a second electron hydration channel (k(B) - 1.3 10(12) s(-1)). The direct characterization of ultr afast electron-atom reactions in polar solutions provide further basis for(i)) the investigation of ultrashort-lived solvent cage effects at the microscopic level, (ii))) a better understanding of quantum branc hing processes during ultrafast electron transfer reactions, (iii)) a knowledge on the role of reorientational correlation function of solve nt molecules around semi-ionized and metastable electronic states.