Kinetic analysis of computer experiments on electron hydration dynamics

Abstract

Instantaneous normal mode analysis of hydrated electron solvation dynamicsAqueous solvation dynamics with a quantum mechanical Solute: Computer simulation studies of the photoexcited hydrated electron

Dynamical Approach to Vibrational Relaxation

“…Furthermore, the value is still more than one order of magnitude smaller than the thermal energy of the solvent, $W= lo3 Jmol-'. This is in marked contrast to the case of hydrated electron where the energy difference is comparable to their own values, 104-105 Jmol-' [97]. Since the energy difference is much smaller than the thermal one in the case of the vibrational relaxation, it is expected that trajectory of the solvent does not depend much on the quantum state.…”

Theoretical Studies of Spectroscopy and Dynamics of Hydrated Electrons

“…The remaining discrepancies between experiment and theory were partly accounted for in subsequent works using flexible water models in MD simulations. 251,252 Not surprisingly, the relaxation was found to take place more rapidly 251,252 than with rigid water models. 250 The direct relaxation to ground state occurs in ~25 fs, while the excited state lifetime was ~160 fs, comparable to some experiments.…”

“…159 This NA technique was first used by Webster et al 250 followed by additional studies 251,252 to explicitly treat nonadiabatic transitions following electron photoionization in neat water. A typical representation of such a NA trajectory can be seen in Figure 13, illustrating non-radiative transition events between excess electron states.…”

“…33,34 Nevertheless, it was argued that the characteristic lifetime should fall between the values found with the rigid model and those with the model that employs classical intramolecular vibrations. 251 A kinetic analysis of the trajectories described the relaxation mechanism 252,253 with a series of fast thermalization steps across the manifold of excited states, followed by competition between a direct trapping channel to the electron ground state and a two-step path involving a welldefined excited hydrated electron state. Nevertheless, we note that the physical identity of the experimentally observed events could not be certain in this photoinjection case.…”

Electron solvation in methanol revisited

“…From the scavenging results (``vertical'' part of the above mechanism) Lewis and Jonah concluded that there is a``fast solvation channel'', A to e À s , and a``slow solvation channel'', B to e À s via e À tr , where A and B are both``dry'' (i.e., nonlocalized) electrons. This idea has been put forward prior to the publication of the results of the ®rst successful diabatic quantum dynamic electron hydration simulations (Webster et al, 1991;Murphrey and Rossky, 1993), and their kinetic analysis, which supported a mechanism much similar to scheme (1) (Keszei et al, 1993;Keszei et al, 1995).…”