Parameters of paramagnetic relaxation were determined by OD ESR and quantum beats techniques for a recombining pair of radical ions (DPS-d10)+/(PTP-d14)− inn-hexane, isooctane,cis-decalin, and squalane solutions. The T2 relaxation time determined by quantum beats technique is independent of solvent viscosity and magnetic field strength in the range 170–9600 G. These data are in agreement with the results obtained by OD ESR technique assuming fastT 1 relaxation for radical cation. Neglecting the contribution of radical anion relaxation, we obtained T1c=T2c≅50 ns for (DPS-d10)+.
Appl.Mag.Res. 1997, V.12, No.4, pp. 505-512

Paramagnetic derivatives of tolan, anthracene, and terphenyl of the A−Sp−R• type, where A is an aromatic group, R• is a stable radical center, and Sp is a spacer, were synthesized. The electronic absorption and luminescence spectra of these compounds were examined. The introduction of the paramagnetic dihydroimidazole fragment causes a decrease (10–500-fold) in the quantum yield of luminescence compared to emission of the individual aromatic luminophore. The presence of a radical center (R•) in the (alkane)•+/−•A−Sp−R• radical-ionic pair leads to the disappearance or fast (nanoseconds) damping of the magnetic effect of luminescence arising upon recombination of these pairs.
Russ.Chem.Bull. 2000, v.49, No.8, pp.1409-1414

Quantum beats caused by the hyperfine coupling (hfc) with magnetically equivalent protons were observed in the recombination fluorescence of the singlet-correlated pairs of secondary radical ions generated in cyclohexane solutions by ionizing radiation. In agreement with theoretical predictions, the ratio IH(t)/I0(t) of fluorescence decay kinetics in high and zero magnetic fields showed narrow peaks for the radical cations with an even number of the equivalent protons. To generate radical pairs, p-terphenyl-d14 was used as an electron acceptor while the solvent holes were trapped by octamethyl-1,4-cyclohexadiene, tetramethylethylene, 9,10-octalin, cis-decalin, hexamethylbenzene, durene, p-diethylbenzene, p-xylene, or benzene. When diisopropylamine was used as a hole acceptor, a trough was observed instead of the strongest peak. The position of the strongest peak (trough) is determined by the value of hfc constant only and is independent of the number of protons.
Chem.Phys. 2000, V.255. No. 2-3, pp.237–245