Production of a fluorescence probe in ion-beam radiolysis of aqueous coumarin-3-carboxylic acid solution-1: Beam quality and concentration dependences
Aqueous coumarin-3-carboxylic acid (3-CCA) solutions were irradiated with seven different ion beams covering LET range from 0.5 to above 2000 eV/nm. G-values of 7OH-CCA, one of hydroxylated products in radiolysis of the solutions, have been determined by fluorescence-HPLC technique in 3-CCA concentration range from 0.1 to 26 mM. The formation yield of 7OH-CCA increased with increase in concentration of 3-CCA while it decreased with increase in LET value of ion beam. Compared with our previous reports on G(∙OH) at a scavenging capacity of 107 s-1 with absorption spectroscopy, it was found that G(7OH-CCA) is about (4.7±0.6)% of G(∙OH), which is consistent for all of the ion beams used in the present study. However, 7OH-CCA yields in high 3-CCA concentration region, especially by using extremely high LET ions, were much higher than expected values based on the above conversion factor and G(∙OH) value predicted in theoretical work.