Electronic Procnsscs in Pulse-irradiated Systems
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Electroniic Processes in Pulse4 rradiated Aqueous and Alcoholic Systems ichael M. Fisher and William H. Hamill* Department of Chemistry and Radiation Laboratory,' University of Notre Dame, Notre Dame, indiana 46556 (Received July 7, 1972)
P ubiica?ioncosts assisted by the U. S. Atomic €nergy Commission
The radiolytic yield of C12- in concentrated neutral aqueous NaCl was not diminished by 1 M NazS04, thereby removing the possible exclusive role of OH in the acid spur. This provides indirect support for H2O C1 which must compete with H20+ H2O H30+ OH, estithe mechanism N2O+ C1mated to occur within sec. Other anions undergo comparable reactions with H20+. The combined yield of 1 2 - and 13- in 1 M KI was decreased -15% by 1 M KCaH302 or 1 M &C204, while h(e2H302OH)/k(I- f OH) = 9.2 x 10-3 and k(C20b2-- OH)/k(I- + OH) = 1.2 X In concentrated aqueous solutions of halide ions, pulse radiolysis appears to form appreciable yields of excited halide ions. In 1-2 M NaCl or 10 M LiC1, at pH -6 and N2 purged, the yield of Clz- was constant for at least 50 nsec, but in NzO-saturated solutions it increased by 20-40% within 60 nsec. The mechanism, may be C1- * i- N2O C1 N2O '. Acetone and Eu3+ produced similar enchancements of the yield of Cia-. The effect of positive hole annihilation by anions on electron yields in ethanol was tested with 10 m M biphenyl, 10 m M pyrene, and 100 m M benzyl acetate. The yields of biphenyl and pyrene anions increased 18 and 25% by addition of 1 M CaC12, the yield of benzyl radical increased 25%. The increased yields of free electrons in alcohol and in water at high concentrations of anions is attributed to electron transfer from the anion to the dry hole (e.g., H20+), thereby preventing electronic hole migration and its contribution to charge recombination.
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Introduction The principal primary species in the radiation chemistry of water are generally considered to be H20*, HzO+, and e - . The hydration of e-- is complete within 10 psec, according to the work of Hunt and his group,2 and may require
