Ion-recombination luminescence in squalane solutions: Spin relaxation effects

Abstract

The luminescence of solutions of p-terphenyl in squalane excited by fast β-particles and its enhancement by magnetic fields has been studied. Applied fields were varied between 1 and 200 mT. Time-resolved single-photon counting was used to measure the luminescence pulse-shapes over a range of 1 µs with a resolution of <1 ns. The decay of the field enhancement at times >200 ns gives a direct measure of the spin–lattice relaxation rate of radical ion pairs. Analysis of the data at shorter times is more difficult but it is shown that relaxation occurs in three stages involving different ion pairs. The reaction mechanism and the nature of the relaxation processes are discussed.