FREE-ION YIELDS FOR SEVERAL SILICON-CONTAINING, GERMANIUM-CONTAINING, AND TIN-CONTAINING LIQUIDS AND THEIR MIXTURES

Free-ion yields have been measured as a function of applied electric field for several room-temperature liquids containing silicon, germanium, or tin atoms. The results show that tetra-alkyl compounds of the same molecular structure have similar free-ion yields independent of the nature of the central group-IV atom. Tetramethylsilane, tetramethylgermane, and tetramethylstannane have similar field-dependent yields. Similarly, tetraethylsilane and tetraethylstannane have comparable yields; the same is true for tetrabutylgermane and tetrabutylstannane. The yields do depend on the nature of the attached alkyl groups: the tetramethyl liquids have higher yields than the tetraethyl liquids, which in turn have higher yields than the tetrabutyl liquids. Fitting the field-dependent free-ion yields to extract a measure of the average thermalization ranges of electrons liberated in the liquids by the ionization process we find that within the precision of our measurements the products of the average electron range times the dielectric constant of the liquid are identical for tetra-alkyl liquids with similar molecular structures. The field-dependent free-ion yields for binary mixtures of high-yield liquid hydrocarbons have also been measured. The yields in these mixtures tend to be less than the yields in either of the pure components. This suggests shorter electron thermalization lengths in mixtures than in pure liquids.