FUNDAMENTAL PROCESSES OF RADIATION-DAMAGE OF BENZENE SOLID STUDIED BYAUGER-ELECTRON PHOTOION COINCIDENCE SPECTROSCOPY

C-H dissociation is known to be responsible for the formation of radia tion damage of hydrocarbon crystals such as color centers or radicals. Recently, Auger electron photoion coincidence (AEPICO) spectroscopy h as allowed us to get detailed information on microscopic processes of radiation damage, because AEPICO spectroscopy can pick up only the fun damental processes, excluding effects due to secondary electrons. In t his work, in an attempt to study which electronic state is responsible for the C-H bond dissociation, AEPICO spectra of benzene solid were m easured at 80 K as a function of photon energy. AEPICO measurements we re examined at three photon energies, i.e. 285 eV (pi(e(2u)) <-- 1s), 287 eV (sigma(C-H) <-- 1s), and 430 eV (ionization <-- 1s). Relative magnitudes of the AEPICO yield Y(hv), which reflects the C-H dissocia tion yield, were estimated by dividing AEPICO signals with intensities of Auger electron yield. Experimental results showed that Y(287 eV)/Y (430 eV) approximate to 1, whereas Y(285 eV)/Y(430 eV) approximate to 0.13. A relation between the small value of Y(285 eV)/Y(430 eV) with t he small values of the radiation damage yield eta(hv) near 285 eV is d iscussed. In that case, eta(near K edge)/< eta(over K edge) approximat e to 0.1 similar to 0.3 [5] [A. Kimura, K. Nakagawa, K. Tanaka, M. Kot ani, R. Katoh, Nucl. Instr. and Meth. in Phys. Res. B91 (1994) 67]. (C ) 1998 Elsevier Science B.V.