SEARCH FOR NEW ROOM-TEMPERATURE LIQUIDS FOR USE IN IONIZATION CHAMBERS

Ionization currents and free ion yields have been measured as a function of applied electric field for ten room temperature liquids containing silicon, germanium, or tin atoms. The highest free ion yields measured are for those liquids having small spherical molecules; tetramethylsilane, tetramethylgermanium, and tetramethyltin. We have updated our earlier measurements for tetramethyltin with a much reduced systematic uncertainty obtained by calculating the contribution to the ionization current from the photoelectric absorption of low energy photons. Tetramethylgermanium and tetramethyltin both have free ion yields similar to tetramethylsilane, making them interesting candidates for use in ionization chambers.