Radical Yields in the Radiolysis of Neutral Aqueous Solutions

Abstract

Abstract The determination of the yields of the two reducing species and the OH radical in the radiolysis of neutral aqueous solutions was undertaken, using deaerated 2-propanol aqueous solutions containing potassium nitrate or hydrogen peroxide as electron scavengers. Irradiation was carried out with 60Co γ-rays, and the hydrogen, nitrite ion, acetone, hydrogen peroxide and pinacol so produced were analyzed. The hydrogen yield decreases upon the addition of hydrogen peroxide or nitrate ions. The yield of hydrogen atoms is found to be 0.61±0.03 by subtracting the molecular yield of hydrogen from the total hydrogen yield in the solutions containing enough scavengers. The yield of nitrite ions increases with an increase in the concentration of nitrate ions, and decreases with an increase in the concentration of acetone and with a decrease in the pH value. The acetone yield increases sharply with an increase in the quantity of nitrate ions and reaches a plateau value in the concentration range of nitrate ions higher than 1×10−2m. In the presence of potassium nitrate of 1×10−2m, pinacol is not formed, and the yield of hydrogen peroxide is less than the molecular yield of hydrogen peroxide. On the basis of these results, radiolysis mechanisms are elucidated and the yields of the hydrated electron and the OH radical of a neutral solution are found to be 2.77±0.03 and 3.0 respectively. The relative rate constants, kH+NO3−⁄kH+(CH3)2CHOH and ke−aq+(CH3)2CO⁄ke−aq+NO−3, are found to be 0.18 and 0.78.