Abstract

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Electronic Dynamics in Aqueous Solutions Studied by Ultrafast UV Photoemission and XAS Spectroscopy

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Electronic Dynamics in Aqueous Solutions Studied by Ultrafast UV Photoemission and XAS Spectroscopy


T. Suzuki1,2*

1Department of Chemistry, Kyoto University, Kyoto, Japan

2suzuki@kuchem.kyoto-u.ac.jp

In this presentation, we report laser-based ultrafast photoemission spectroscopy and XFEL-based ultrafast X-ray absorption spectroscopy of aqueous solutions. UV and VUV photoemission spectroscopy of liquid microjets enables observation of valence electron dynamics in aqueous solution within the depth less than several nanometers from the surface. Appropriate solute concentration minimizes electrokinetic charging of liquids and enables reliable measurements of electron binding energies. Time-and angle-resolved photoemission spectroscopy of liquid microjets is performed using a linear time-of-flight spectrometer and polarization rotation of the probe pulse (50 – 100 kHz). Anisotropic photoemission from photoexcited solute and isotropic photoemission from hydrated electron were observed. SACLA is a hard X-ray free electron laser constructed in Japan. Time-resolved XAS was performed for [Fe(III)(C2O4)3]3- in water near the Fe K-edge. The Fe K-edge exhibited red-shift upon 268-nm excitation with two time-constants of 140 fs and 3 ps, and the EXAFS feature has diminished. The analysis aided by DFT calculations indicate photoreduction of Fe(III) via LMCT transition, followed by the release of CO2- which induces a secondary reducing reaction of unexcited [Fe(III)(C2O4)3]3-.

References:

[1] Y. Suzuki, K. Nishizawa, N. Kurahashi and T. Suzuki, Phys. Rev. E 90, 010302 (2014).

[2] N. Kurahashi, S. Karashima, Y. Tang, T. Horio, B. Abulimiti, Y. Suzuki, Y. Ogi, M. Oura and T. Suzuki, J. Chem. Phys. 140, 174506 (2014).

[3] Y. Yamamoto, Y. Suzuki, G. Tomasello, T. Horio, S. Karashima, R. Mitric and T. Suzuki, Phys. Rev. Lett. 112, 187603 (2014).

[4] S. Adachi, T. Horio and T. Suzuki, Opt. Lett. 37, 2118 (2012).

[5] Y. Ogi et al., Structural Dynamics submitted (2015)