Significant role of secondary electrons in the formation of a multi-body chemical species spur produced by water radiolysis

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

Scientific insight of water radiolysis is essential to estimate the direct and indirect effects of radiation DNA damage. Secondary electrons produced by water radiolysis are responsible for both effects. Here, we use a first-principles code to calculate the femtosecond dynamics of secondary electrons produced as a result of 20-30 eV energy deposition to water and analyze the formation mechanism of radiolytic chemical species produced in a nano-size ultra-small space region. From the results, it was clarified that the chemical species produced by water radiolysis begin to densify in the ultra-small region of a few nanometers when the deposition energy exceeds 25 eV. Our results provide important scientific insights into the formation of clustered DNA damage, which is believed to cause biological effects such as cell death.