title: Ultrafast dynamics of room temperature ionic liquids after ultraviolet femtosecond excitation.
abstract: The photochemistry and relaxation dynamics of four room-temperature ionic liquids (RTILs) after ultraviolet (UV) photolysis were investigated by femtosecond pump-probe absorption spectroscopy. A pulse duration-limited rise of the induced absorption in halide-containing RTILs at various probe wavelengths was attributed to the generation of solvated electrons. With continuous irradiation (static conditions), di- and trihalide ion formation became apparent especially below 1000 nm. The formation of trihalide ions was further confirmed by steady-state UV absorption spectroscopy. All RTILs showed a rich photochemistry after UV photolysis leading to the build-up of various long-lived intermediate products as evidenced from the observation that ionic liquids turn yellow upon continuous irradiation. On the other hand, exposing RTILs to the excitation pulse for a short time (rapid-scan method) significantly suppressed the formation of halides. The results suggest that the development of flow-cell systems for highly viscous ionic liquids is urgently needed to quantitatively investigate their ultrafast dynamics.
authors.affiliation: Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Universität Karlsruhe, Kaiserstr. 12, D-76128 Karlsruhe, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Brands
authors.forename: N
authors.initials: N
authors.lastname: Chandrasekhar
authors.forename: A-N
authors.initials: AN
authors.lastname: Unterreiner