PRIMARY EVENTS FOLLOWING ELECTRON INJECTION INTO WATER AND ADSORBED WATER LAYERS

The initial stages of the evolution of an electron injected into bulk water (at 300 K) and into thin water films (1-4 monolayers) adsorbed on a Pt(111) substrate at 50 K are investigated. It is shown that for electrons injected into bulk water with an initial translational kinetic energy between 1.54 and 6.18 eV (i.e., subexcitation energies), the electron momentum time-correlation function 〈p̂(0)p̂(t)〉, decays to zero on a time scale of less than 1 fs, reflecting strong backscattering of the electron by the water molecules. On this time scale the electron propagation in the medium is dominated by elastic processes. Furthermore, during this initial stage the system is well represented by a static aqueous medium. Transmission of electrons injected into thin films of adsorbed water is also dominated by elastic scattering. The dependence of the electron transmission probability on the film thickness and the initial injection energy are in accord with recent experimental results of photoinjected electrons into adsorbed water films. © 1990 American Institute of Physics.