Dissociative electron attachment in water and methanol (5–14 eV)

Abstract

Energies of D^– and O^– ions produced by dissociative electron attachment (DA) to D₂O and CD₃OD (and some partially deuteriated methanols) over three resonance regions (ca. 6.5, 8.5 and 10.5 eV) are reported. In both water and methanol over the first two resonances, the most probable D^– ion energy is close to the maximum possible, following rupture of the O—D bond to give ground-state products. Over the same two resonances in water, O^– ions appear to be produced in a symmetric dissociation accompanied initially by highly excited D₂ and, then, above the appropriate energy threshold, by D atoms. Dissociative pathways for the highest energy resonances are not established, but in methanol, the available experimental evidence points to dissociation from a relatively long-lived, rearranged complex (possibly CD₂OD^–₂). Attention is drawn, where comparison is possible, to similarities between the dissociative behaviour of anions (electron/molecule resonant states) and photodissociation of the parent neutral states.