Adsorbate dissociation due to heteromolecular electronic energy transfer from fluorobenzene thin films

• Published in: Physical chemistry chemical physics : PCCP 2024-04, Vol.26 (15), p.1191-11921
• Main Author: Jensen, E. T
• Format: Article
• Language: English
• Subjects: Benzene; Excitons; Incident light; Kinetic energy; Photoabsorption; Photodissociation; Photoexcitation; Substrates; Thin films
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d3cp05520e

Study of the near-UV photodissociation dynamics for monolayer (ML) quantities of CH 3 I on thin films of a series of fluorobenzenes and benzene (1-25 ML) grown on a Cu(100) substrate finds that in addition to gas-phase-like neutral photodissociation, CH 3 I dissociation can be enhanced via electronic energy transfer to the CH 3 I following photoabsorption in several of the thin films studied. Distinct CH 3 photofragment kinetic energy distributions are found for CH 3 I photodissociation on C 6 H 5 F, 1,4-C 6 H 4 F 2 and C 6 H 6 thin films, and distinguished from neutral photodissociation pathways using polarized incident light. The effective photodissociation cross section for CH 3 I on these thin films is increased as compared to that for the higher F-count fluorobenzene thin films due to the additional photodissociation pathway available. Quenching by the metal substrate of the photoexcitation via this new pathway suggests a significantly longer timescale for excitation than that of neutral CH 3 I photodissociation. The observations support a mechanism in which neutral photoexcitation in the thin film ( i.e. an exciton) is transported to the interface with CH 3 I, and transfers the electronic excitation to the CH 3 I which then dissociates. The unimodal CH 3 photofragment distribution and observed kinetic energies on the fluorobenzene thin films suggest that the dissociation occurs via the 3 Q 1 excited state of CH 3 I. Near-UV photodissociation of CH 3 I on various fluorobenzene thin films grown on Cu(100) finds that dissociation can be enhanced via electronic energy transfer to the CH 3 I following photoabsorption in several of the thin films.