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

测量<mu>了超临界正-（n-B）、异丁烷（i-B）、正-（n-P）、异-（i-P）和新戊烷（neoP）中过剩电子的迁移率和导电态能量Vo与密度N的关系<mu>。Vo值最初在N=0时从零开始减小，然后随着N而增大。升高温度会导致<mu>N最小值向低N在所有的碳氢化合物，但最大值向低N仅在n-B和n-P。在其他更对称的碳氢化合物的最大值的轨迹是独立的温度。在n-B和n-P包括温度依赖性的最小值是充分再现的Cohen-Lekner模型与使用的结构因子估计从声速。在i-B，i-P和neoP的模型预测的最小值的发生在一个更高的密度比观察到的，和散射截面的大小与N的变化必须调用，在这些烃的对应Vo最小值和<mu>N最大值的观察，这表明，变形潜力的最小值是最大值的出现的原因。在直链碳氢化合物中的最大值是由于从准自由到局部电子状态的过渡所造成的增加的重要性，在更高的密度的不对称分子的配位数和取向的波动。研究电介质中过量电子的下一步是研究<mu>更高密度区域（高压下）中的Vo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.