Effect of a magnetic field on the fluorescence produced in irradiated anthracene solutions

Abstract

The effect of an applied magnetic field on the fluorescence from radiolytic ion recombination has been studied for anthracene in some hydrocarbon solvents. In pulse-irradiated anthracene (10−2 mol dm−3) in squalane, the fluorescence intensity following the pulse increases as a function of applied magnetic field in the range studied, 0 to 0.3 T (0 to 3000 G). At a constant magnetic field strength, the field-induced enhancement of the fluorescence intensity varies with time after the pulse. At high field strengths (0.3 T) the enhancement reaches a maximum of ∼45% about 50 ns after the pulse. Similar effects are observed in cyclohexane but the enhancement is smaller than that in squalane. In benzene solutions the effect is extremely small. These findings are confirmed by observations in continuously gamma-irradiated solutions. In gamma-irradiated solutions of anthracene (10−2 mol dm−3) in squalane, the fluorescence intensity increases with increasing magnetic field and approaches ∼13% enhancement at high fields (>0.1 T). The enhancement is smaller (∼3%) in cyclohexane and very small (<1%) in benzene solutions. 9,10-Dimethylanthracene gives a larger enhancement and anthracene-d10 a smaller enhancement than the parent anthracene at high fields. The results are in general agreement with recent theoretical predictions based on the effect of a magnetic field on the loss of spin correlation of geminate ions pairs prior to recombination.