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Updated: Jul 17, 2026

An Experimental Protocol for Femtosecond NIR/UV - XUV Pump-Probe Experiments with Free-Electron Lasers
Published on: October 23, 2018
Ultrafast dynamics of room temperature ionic liquids after ultraviolet femtosecond excitation
H Brands1, N Chandrasekhar, A-N Unterreiner
1Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Universität Karlsruhe, Kaiserstr. 12, D-76128 Karlsruhe, Germany.
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.
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