PHOTOCURRENTS IN NEAT METHANE AND ETHANE

Photocurrents appear in neat liquid methane for photon energies hv>11.3 eV. In neat ethane gas, the photoconductivity threshold decreases with density rho from 11.5 eV at rho=3X10(16) cm(-3) to 10.85 eV at rho=2.2X10(21) cm(-3). It continues to decrease, though more slowly, in the liquid. Moreover, in liquid C2H6 an increase in the field strongly enhances the photocurrent, the degree of enhancement depending on the photon energy. No such enhancement was observed in liquid methane. The results are discussed with reference to known values of excess electron energies V-0 and electron mobilities mu(e), and in view of recent simulation results [L. Liu and B.J. Berne, J. Chem. Phys. 99 (1993) 9054] on electron solvation in both substances.