Electron mobilities and electron–ion recombination rate constants in solid, liquid, and gaseous methane

Abstract

Electron mobilities and electron–ion recombination rate constants have been measured in methane by an x-ray pulse conductivity technique over the density region from 2×1020 to 1.9×1022 molecules/cm3 including the critical region and the liquid–solid phase change. The observed electron mobility abruptly increases on the transition from liquid to solid, which is probably due to the change of isothermal compressibility of methane on the phase change. The observed electron–ion recombination rate constant is in good agreement with the value calculated by the reduced Debye equation in solid methane but not in liquid and gaseous methane. The deviation from the reduced Debye equation is larger in the gas phase than in the liquid phase, which is probably caused by the difference in the efficiency of excess-energy loss of electrons within the reaction radius of electron–ion recombination.