The induction of quantum beats by hyperfine interactions in radical-ion pair recombination

Quantum beats were detected in the recombination of spin-correlated radical-ion pairs. These beats are induced by singlet-triplet transitions in a pair due to hyperfine interactions. Singlet radical-ion pairs were generated by radiolysis of hydrocarbons involving acceptors of electrons and holes. The singlet pair recombination was detected by the luminescence of the product (singlet-excited molecules). The beat frequencies measured for (tetramethylethylene) ⁺/(paraterphenyl-d₁₄)-and (durene)⁺/(paraterphenyl-d₁₄)^? pairs correspond to the hfi constants in the cation radicals. The character of the beats differ in high and zero magnetic fields and their shape depends upon the solvent.