Ion yields for tetramethylgermane exposed to X-rays near the GeK-edge

Free ion yields were measured for tetramethylgermane (TMG) in both the liqu id and vapor phase and for Kr gas exposed to X-rays: The X-ray energy was v aried across the K-edges of Ge and Kr, respectively. In Kr the relative W v alue increases slightly at the K-edge, which is at 14.3 keV. In liquid TMG the observed ion yield drops at the Ge K-edge (11.1 keV) and shows two mini ma separated by 10 eV. This ion-yield spectrum is a mirror image of the abs orption spectrum, as represented by the gas-phase ion-yield spectrum. The o bservation of such an inverted spectrum in liquids is shown to be due in la rge part to inefficiency of collection of charges. This is a consequence of the large Ge cross sections above the edge which concentrates the region o f irradiation near the entrance window, increasing the local dose rate and enhancing recombination. The yield of excited states in mixtures of TMG and toluene drops at the Ge K-edge by the amount expected considering the larg e X-ray fluorescence yield.