Reactions in spurs: mechanisms of hydrated electron formation in radiolysis of water

Abstract

Hydrated electron and solute anion formation in H₂O and D₂O has been investigated with the picosecond pulse radiolysis technique. The spectrum of e^–_aq in D₂O is slightly shifted towards the blue as compared with that in H₂O. The yields of e^–_aq in liquid H₂O and D₂O are larger than those of e^– in the corresponding vapours. Use of salicylate anion (Sal_aq) as an electron scavenger shows that the yields of its electron adduct (Sal^–_aq) are considerably larger than those of the e^–_aq. The importance of electronically excited water molecules in the formation of these extra yields in indicated. Three possible mechanisms to explain the extra yields are considered: (i) solvent assisted e^–_aq formation from excited water; (ii) energy transfer from excited water to OH^–_aq leading to e^–_aq formation; the OH^–_aq is postulated to result from ionic dissociation of vibrationally excited water molecules in spurs; and (iii) interaction of Sal_aq and excited water to produce Sal^–_aq.