Investigations of the biological effects of radiation: a multi-discipline approach. Progress report, September 1, 1976--August 31, 1977

The quasi-free electron attachment rate, k/sub e/, and mobility, μ/sub e/, were studied in non-polar solutions using pulsed conductivity techniques. Measurements of k/sub e/ of >50 nitro compounds in liquids have μ/sub e/ ranging from <0.1 to 100 cm2/volt sec at temperatures from -100 to +400C indicated electron-dipole interactions are important in liquids having μ/sub e/ < 1 cm2/volt sec. The Smoluchowski equation was modified to include electron-dipole interactions and calculated k/sub e/'s agreed with observations within +-20%. The cellular enhancement ratio, CER, of nine of the nitro compounds were measured and a correlation between k/sub e/ and CER was found which was used to refine a model of cellular radiosensitization involving quasi-free electrons. Diffusion-controlled k/sub e/'s were observed for several carcinogens and in reversed micellar solutions. Field-dependent k/sub e/'s were measured in liquids having μ/sub e/ ranging from 10-4 to 500 cm2/volt sec and were found to increase at μ/sub e/ < 1 and decrease at μ/sub e/ > 70 cm2/volt sec with increasing field. The μ/sub e/ of liquid C2H6 was measured from -400C through the critical temperature at fields up to 180 kV/cm and a transition from polaron to delocalized electron conduction was observed. A pico-second (ps) pulse conductivity technique was developed and hot electron and/or autoionization processes were observed in tetramethylsilane, TMS, 200 ps after the ionizing pulse. A dose, field, and polarity dependent conductivity spike having a lifetime of 100 ps was observed in TMS and is interpreted as a prebreakdown phenomenon