TOTAL IONIZATION AND RANGE OF LOW-ENERGY RECOIL PARTICLES IN PURE AND BINARY GASES

The total ionization and range of the 103-keV Pb206 recoil particle that results from the decay of Po210 deposited on a metallic backing have been determined for a number of gases. The method employed a hemispherical ion chamber and a vibrating-reed electrometer. The 5.3-MeV particles were used for calibration. The gases used were Ne, Ar, Xe, N2, dry air, CH4, C2H4, 95% Ar+5% C2H4, and other binary mixtures. The equivalent range, in microns, of the Pb206 particle in the listed gases at STP is 131, 79, 44, 80, 83, 84, 58, and 82, respectively. The uncertainty in each value is 2. The average energy loss per ion pair produced, Wr, in eV/(ion pair), for the Pb206 particle in passing through the gases, omitting Ne, is 1216, 1588, 1166, 1206, 1216, 1154, and 81.72, respectively. Theory and experiment for the range of the Pb206 particle in the monatomic gases lie within 5% of each other. A rough calculation is made of the energy the recoil particle loses through molecular, nonionizing processes per ion pair produced. For N2 this amounts to approximately 10 eV/(ion pair) of the Wr value. © 1968 The American Physical Society.