Electron thermalization distances and free ion yields in liquid nitrogen from 77 K to near T/sub c/

The free ion yield in x-irradiated liquid nitrogen at zero applied field strength increases from G0/sub fl/ = 0.0034 ion pairs/100 eV at 77.1 K to 0.043 at 123.7 K, while the density-normalized thermalization distance of the secondary electrons increases from b/sub E//sub P/d = 4.4 x 10-6 to 5.6 x 10-6 kg/m2. The ratio of the G/sup E//sub f//sub i/ values at 123.7 and 77.1 K decreases from 13 at E = 0 to 3.1 at E = 5.2 MV/m. Yields calculated from the extended Onsager model agree with the measured values only when the electron thermalization distance distribution is assumed to be exponential with an added power tail (YEP): F(y) = YE, 0<(y-y0)<3.5b/sub E//sub P/; F(y) = YE+0.74b2/sub E//sub P//(y-y0)3, (y-y0)>3.5b/sub E//sub P/; where YE = b/sup -1//sub E//sub P/ exp[(y0-y)/b/sub E//sub P/], y>y0. The electron thermalization process in liquid nitrogen appears to be truncated by electron capture to form an anion