Dense radical formation in deuterated alanine by 1.5 keV soft X-ray irradiation

Nakagawa, Seiko*; Oka, Toshitaka   ; Fujii, Kentaro*; Yokoya, Akinari*

Radicals produced in crystalline L-alanine-3,3,3-d3 and L-alanine-d4 were observed by the electron spin resonance (ESR) technique during 1.5 keV soft X-ray irradiation. The line width of the ESR spectra obtained by the soft X-ray irradiation was 1.5 times wider than that of hard X-rays. The efficiency of the radical yield by the soft X-ray irradiation was 10 relative to that by -irradiation. The product formed by the radical recombination was observed by an LC/MS analysis. For the soft X-ray irradiation, many radicals will be lost by the efficient radical-radical recombination due to the higher density of the radicals, just as the high-LET irradiation by heavy ions.