Determination of the time-dependent OH-yield by using a fluorescent probe. Application to heavy ion irradiation

This Letter reports a sensitive method using HPLC-Fluorescence detection of •OH in liquid water under high-energy heavy ion irradiation. The coumarin-3-carboxylic-acid (3CCA) molecule was selected for probing •OH and providing the fluorescent 7-hydroxy-coumarin-3-carboxylic-acid (7OH-3CCA). Since the concentration limit achievable is better than 1 nM, the radiolytic yields were determined with a sensitivity of 2 × 10−9 mol/J for 4.8 GeV-12C6+ of and 20 GeV-40Ar18+ in the ns time range. They decrease with the linear energy transfer from 2.8 × 10−7 to 1.3 × 10−7 mol/J (C6+ of 11 eV/nm) and 1.5 × 10−7 to 0.9 × 10−7 mol/J (Ar18+ of 90 eV/nm) which is in agreement with the literature data.