Electron Impact Relative Ionization Cross Sections and Fragmentation of U, UO, UO2, and UO3

Abstract

Electron impact relative ionization cross sections and fragmentation patterns of U, UO, UO₂, and UO₃ have been measured using 4–60‐V electrons. Because the molecules are extensively fragmented, both total relative ionization cross sections and cross sections for production of parent ions are given. Values are tabulated as a function of ionizing voltage. The total cross sections at 40 V fail to conform to the additivity rule with the cross section of UO₃ about half of that for U. Five volts above threshold, the total cross section ratio of UO₃ to U is 0.08. Because of UO₃ fragmentation, a smaller ratio in terms of parent ions of 0.025 is found. All three oxide molecules are severely fragmented by electron impact. At 40 V 85% of the ions produced from UO₃ are fragments. For the U‐O system, use of theoretical atomic ionization cross sections and the additivity rule leads to sizeable errors at high voltages and far greater errors at low voltage.