Mechanisms for the Near-UV Photodissociation of CH${}_3$I on D${}_2$O/Cu(110)

Abstract

The system of CH${}_3$I adsorbed on submonolayer, monolayer and multilayer thin films of D${}_2$O on Cu(110) has been studied by measuring the time-of-flight (TOF) distributions of the desorbing CH${}_3$ fragments after photodissociation using linearly polarized $\lambda$=248nm light. For multilayer D${}_2$O films (1-120ML), the photodissociation is dominated by neutral photodissociation via the "A-band" absorption of CH${}_3$I. The polarization and angle dependent variation in the observed TOF spectra of the CH${}_3$ photofragments find that dissociation is largely via the ${}^3{Q}_0$ excited state, but that also a contribution via the ${}^1{Q}_1$ excitation can be identified. The photodissociation results also indicate that the CH${}_3$I adsorbed on D${}_2$O forms close-packed islands at submonolayer coverages, with a mixture of C-I bond axis orientations. For submonolayer quantities of D${}_2$O we have observed a contribution to CH${}_3$I photodissociation via dissociative electron attachment (DEA) by photoelectrons. The observed DEA is consistent with delocalized photoelectrons from the substrate causing the observed dissociation -- we do not find evidence for a DEA mechanism via the temporary solvation of photoelectrons in localized states of the D${}_2$O ice.

References in corpus (1)

• Charge-transfer photodissociation of adsorbed molecules via electron image states

Cited by in corpus (1)

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