Excess electrons in dense hydrocarbon gases: The effect of molecular shape on electron mobilities.

测量了超临界n-(n- b)、异丁烷（i-B）、n-(n- p)、异-(i-P)和新戊烷（neoP）中多余电子的迁移率<mu>和导电态能Vo随密度n的变化，随着n的增加，所研究的所有碳氢化合物的密度归一化迁移率<mu >n在低于各自临界密度时经历一个最小值，然后增加到最大值。在N=0时，Vo值先从零开始下降，然后随着N的增加而增加。温度升高导致所有烃类中<mu> N的最小值向低N方向移动，但最大值仅在N - b和N - p中向低N方向移动。在其他更为对称的碳氢化合物中，极大值的位置与温度无关。Cohen-Lekner模型利用从声速估计的结构因子充分再现了n-B和n-P中包括温度依赖的最小值。在i-B、i-P和neoP中，模型预测的最小值出现在比观测到的密度更高的地方，散射截面的大小随N的变化必须被引用。在这些碳氢化合物中，观察到Vo最小值和<mu> N最大值的对应关系，这表明变形势的最小值是出现最大值的原因。直链烃中的最大值是由准自由电子态向局域电子态的转变引起的，这种转变是由不对称分子的配位数和取向的波动在较高密度下的重要性增加引起的。介电介质中多余电子研究的下一步是研究<mu>和Vo在更高密度区域（高压下）的行为，目的是收集有关局域态性质的信息。

The mobility <mu> and the conducting state energy Vo of excess electrons in supercritical n-(n-B), isobutane(i-B), n-(n-P), iso-(i-P) and neopentane(neoP) were measured as a function of density N, With increase in N,the density-normalized mobility <mu> N in all hydrocarbons studied goes through a minimum at a density below the respective critical density, and then increases to a maximum. Vo values initially decrease from zero at N=0, and then increase wth N. Raising temperature causes <mu> N minima to shift toward lower N in all hydrocarbons, but the maxima shift to lower N only in n-B and in n-P. In other more symmetrical hydrocarbons the loci of maxima are independent of temperature. The minima in n-B and n-P including temperature dependence is adequately reproduced by the Cohen-Lekner model with the use of the structure factor estimated from the speed of sound. In i-B,i-P and neoP the model predicts the occurrence of the minima at a higher densities than are observed, and changes in the magnitude of scattering cross section with N have to be invoked, In these hydrocarbons the correspondence of Vo minima and <mu> N maxima is observed, which indicates that the minima of the deformation potentials are the cause for the appearance of the maxima. The maxima in the straight-chain hydrocarbons are due to the transition from the quasifree to the localized electron states caused by the increased importance at higher densities of fluctuations in coordination numbers and orientations of unsymmetrical molecules. The next step of the study of excess electrons in dielectric media is to investigate <mu> and Vo behavior in a still higher density region (under high pressure) with the aim to gather information concerning the nature of localized states.