First-principles simulation of an ejected electron produced by monochromatic deposition energy to water at the femtosecond order

Takeshi Kai; Tomohiro Toigawa; Yusuke Matsuya; Yuho Hirata; Tomoya Tezuka; Hidetsugu Tsuchida; Akinari Yokoya

doi:10.1039/d3ra05075k

First-principles simulation of an ejected electron produced by monochromatic deposition energy to water at the femtosecond order

RSC Adv. 2023 Nov 3;13(46):32371-32380. doi: 10.1039/d3ra05075k. eCollection 2023 Oct 31.

Authors

Takeshi Kai¹, Tomohiro Toigawa¹, Yusuke Matsuya^{1

2}, Yuho Hirata¹, Tomoya Tezuka³, Hidetsugu Tsuchida^{3

4}, Akinari Yokoya⁵

Affiliations

¹ Nuclear Science and Engineering Center, Japan Atomic Energy Agency 2-4 Shirane Shirakata, Tokai-mura, Naka-gun Ibaraki 319-1195 Japan.
² Faculty of Health Sciences, Hokkaido University Kita-12 Nishi-5, Kita-ku Sapporo Hokkaido 060-0812 Japan.
³ Department of Nuclear Engineering, Kyoto University Nishikyo-ku Kyoto 615-8530 Japan.
⁴ Quantum Science and Engineering Center, Kyoto University Gokasho, Uji Kyoto 611-0011 Japan.
⁵ Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage-ku Chiba-shi 263-8555 Japan.

Abstract

This study uses a time-dependent first-principles simulation code to investigate the transient dynamics of an ejected electron produced in the monochromatic deposition energy from 11 to 19 eV in water. The energy deposition forms a three-body single spur comprising a hydroxyl radical (OH˙), hydronium ion (H₃O⁺), and hydrated electron (e_aq^-). The earliest formation involves electron thermalization and delocalization dominated by the molecular excitation of water. Our simulation results show that the transient electron dynamics primarily depends on the amount of deposition energy to water; the thermalization time varies from 200 to 500 fs, and the delocalization varies from 3 to 10 nm in this energy range. These features are crucial for determining the earliest single-spur formation and facilitating a sequential simulation from an energy deposition to a chemical reaction in water photolysis or radiolysis. The spur radius obtained from the simulation correlates reasonably with the experimental-based estimations. Our results should provide universalistic insights for analysing ultrafast phenomena dominated by the molecular excitation of water in the femtosecond order.