Excess electron mobility in liquid methane and ethane

The elucidation of the primary processes in the interaction of high energy radiation with condensed matters is the main interest in studying the physico-chemical properties of excess electrons in liquid hydrocarbons. The properties of highly mobile excess electrons in liquid hydrocarbons are strongly influenced by the structure of the molecules composing the liquid, and the influence was dramatically demonstrated by the comparison of the electron mobility in liquid methane and ethane. For instance, at 111 K in liquid methane, the electron mobility of 400 cm2/Vs was found, while at the same temperature, the mobility in liquid ethane was 1.3 x 10-3 cm2/Vs. The measurement of short time signals requires careful consideration of the resonance properties of the measurement gap. The dimensions of such measurement gap are such that the response of the cell is less than 1 ns. Faster response time can be obtained by decreasing the gap capacitance, which can be achieved either by increasing the electrode separation or by decreasing their cross section. The increase of mobility with temperature is mainly caused by the decrease in liquid density and its effect on the effective mass. Pressure rises with temperature, and the compressibility and the influence of fluctuation decrease. At higher density, localization is energetically more favorable, while at lower density, the electrons are delocalized. (Yamashita, S.)