Direct time-resolved measurement of radical species formed in water by heavy ions irradiation

Time-resolved absorption spectroscopy has been used to detect radical species in water ionised by swift heavy ions. These experiments have been performed at the GANIL cyclotron (Caen-France) with C-12(6+) (75 MeV/A) and S-36(16+) (77 MeV/A) particles whose linear energy transfer (LET = -(dE/dx)(elec) is respectively two and three orders of magnitude greater than electron or gamma rays. The chemistry in water is thus considerably modified at the first moments after the ionisation. In particular the radiolytic yields of the radicals like hydrated electron decrease when the LET is increasing. The temporal structure of the beam is used to perform time-resolved spectroscopy of the transient radicals formed by water radiolysis within the microsecond time scale. It is possible to show the inhomogeneous chemistry around the ion tracks and to compare these results with the Monte Carlo simulations. (C) 1998 Published by Elsevier Science B.V. All rights reserved.