Delayed fluorescence detected magnetic resonance study on the spin dynamics of the transient radical-ion pair formed in the photolysis of carbazole in 2-propanol

A delayed fluorescence detected magnetic resonance method is applied to the study of a transient radical-ion pair (RIP) formed in the photolysis of carbazole in 2-propanol. The spectra under different microwave powers are analyzed with a simple quantum-mechanical model calculation. The experimental and calculated data prove that the formation of the RIP (carbazole cation and solvated electron) is by way of a biphotonic process and the initial spin state of the RIP is the singlet. It is shown that no strong interaction such as exchange between the component ion radicals exists, which implies the large separation of the ion radicals immediately after their birth. The spectrum of the RIP having a solvated electron as the counter radical shows the characteristic shape of spin locking at high microwave power.