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Journal Articles

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

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

RSC Advances (Internet), 13(46), p.32371 - 32380, 2023/11

Although scientific knowledge of photolysis and radiolysis of water is widely used in the life sciences and other fields, the formation mechanism of the spatial distribution of hydrated electrons (spur) resulting from energy deposition to water is still not well understood. The chemical reaction times of hydrated electrons, OH radicals, and H$$_{3}$$O$$^{+}$$ in the spur strongly depend on the spur radius. In our previous study, we elucidated the mechanism at a specific given energy (12.4 eV) by first-principles calculations. In the present study, we performed first-principles calculations of the spur radius at the deposition energies of 11-19 eV. The calculated spur radius is 3-10 nm, which is consistent with the experimental prediction (~4 nm) for the energy range of 8-12.4 eV, and the spur radius gradually increases with increasing energy. The spur radius is a new scientific knowledge and is expected to be widely used for estimating radiation DNA damage.

Journal Articles

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation

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

RSC Advances (Internet), 13(11), p.7076 - 7086, 2023/03

 Times Cited Count:1 Percentile:84.66(Chemistry, Multidisciplinary)

Scientific insights of water radiolysis are widely used in the life sciences and so on, however, the formation mechanism of radicals, a product of water radiolysis, is still not well understood. We are challenging to develop a simulation code to solve this formation mechanism from the viewpoint of radiation physics. Our first-principles calculations have revealed that the behavior of secondary electrons in water is governed not only by collisional effects but also by polarization effects. Furthermore, from the predicted ratio of ionization to electronic excitation, based on the spatial distribution of secondary electrons, we successfully reproduce the initial yield of hydrated electrons predicted in terms of radiation chemistry. The code provides us a reasonable spatiotemporal connection from radiation physics to radiation chemistry. Our findings are expected to provide newly scientific insights for understanding the earliest stages of water radiolysis.

Journal Articles

Convergence behavior in line profile analysis using convolutional multiple whole-profile software

Kumagai, Masayoshi*; Uchida, Tomohiro*; Murasawa, Kodai*; Takamura, Masato*; Ikeda, Yoshimasa*; Suzuki, Hiroshi; Otake, Yoshie*; Hama, Takayuki*; Suzuki, Shinsuke*

Materials Research Proceedings, Vol.6, p.57 - 62, 2018/10

 Times Cited Count:0 Percentile:0.18

Journal Articles

Isoscalar giant resonances in the Sn nuclei and implications for the asymmetry term in the nuclear-matter incompressibility

Li, T.*; Garg, U.*; Liu, Y.*; Marks, R.*; Nayak, B. K.*; Madhusudhana Rao, P. V.*; Fujiwara, Mamoru*; Hashimoto, Hisanobu*; Nakanishi, Kosuke*; Okumura, Shun*; et al.

Physical Review C, 81(3), p.034309_1 - 034309_11, 2010/03

 Times Cited Count:100 Percentile:97.44(Physics, Nuclear)

Oral presentation

Computer simulation of the earliest processes of radiation biological effects of; Direct and indirect effects of DNA damage

Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke; Hirata, Yuho; Tezuka, Tomoya*; Tsuchida, Hidetsugu*; Ito, Yuma*; Yokoya, Akinari*

no journal, , 

Irradiation of living systems forms complex DNA damage that induces biological effects in very rare cases. This complex DNA damage is called cluster damage and is very difficult to detect experimentally. In this study, we have developed physical and chemical codes for analyzing DNA damage, and are working to elucidate the formation mechanism of cluster damage. In this study, we analyzed the results of calculations in a simple system in which energy is deposited to DNA and secondary electrons are emitted, and showed that the formation mechanism of cluster damage strongly depends on the deposition energy to DNA. This scientific insight is expected to contribute to the elucidation of the repair mechanism of DNA damage and lead to the elucidation of radiation biological effects.

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