Low-energy auger- and photo-electron effects on the degradation of thymine by ultrasoft X-irradiation

Akamatsu, Ken; Fujii, Kentaro; Yokoya, Akinari

The productions of stable/unstable thymine radicals produced by monochromatic ultrasoft X (USX)- or Co -rays were studied using EPR spectroscopy. EPR experiment of thymine was performed using a newly developed X-band EPR device installed in a JAERI soft X-ray beamline (BL23SU) in SPring-8. The sample pellet was irradiated with USX photons at a microwave in a vacuum chamber. EPR measurements of a thymine powder pellet irradiated with USX around 500 eV at 77 K and RT. As a reference, Co g-irradiation to the pellet was also performed at RT. As the results, following three findings are obtained: (1) An unstable radical appearing only in situ USX-irradiation is observed. And the radical is clearly distinguished with other stable radicals remaining after irradiation. (2) The signal of the unstable radical is a strong singlet, which vanishes after irradiation immediately.