Tuning the ion formation processes from triplet–triplet annihilation to triplet-mediated photoionization

• Published in: Chemical physics letters Vol. 378; no. 1; pp. 185 - 191
• Main Authors: Jacques, P., Allonas, X., Sarbach, A., Haselbach, E., Vauthey, E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 29.08.2003; Elsevier Science
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Chemical solution; Ultraviolet irradiation; Photoionization; Oxidation potential; Triplet triplet annihilation; Ionization potential; Tunable laser; Photochemical reaction; Photoconductivity; Ketone; Organic compounds; Excited state
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(03)01211-9

Free ion formation in acetonitrile is examined through transient photoconductivity for a set of ketones excited at different wavelengths. According to the photophysical parameters of the ketones and the incident photon energy, two mechanisms can be operative: triplet–triplet annihilation (bimolecular process) and/or photoionization (monomolecular biphotonic process). By using a tunable laser, excited state mediated photoionization was studied. From the threshold energy ( E thr) required for this process to occur, ionization potentials in solution ( I S) were deduced and compared to the corresponding values in gas phase ( I G). A simple energetic model enables the determination of the oxidation potential ( E ox) of the ketones that are compared to the corresponding values obtained through electrochemical measurements.