An Analysis of S-T0 Mixing Polarization of CIDEP in Terms of the Lennard-Jones Fluids: 1-Hydroxy-1-methylethyl Radical in 2-Propanol

Abstract

Abstract Calculations of the magnitudes of the polarization (PRPM) due to singlet-triplet (S-T0) mixing of the radical pair mechanism of chemically induced dynamic electron polarization (CIDEP) are made by numerically solving the stochastic Liouville equations for fluids in which intermolecular interactions are represented by the Lennard-Jones (LJ) potentials. PRPM and the relation between PRPM and the difference in the resonance frequencies of radicals of the pair (2Qab) are examined for the continuum and for various models with different relative strengths of solute-solute, solute-solvent, and solvent-solvent interactions.In the continuum, PRPM reaches the maximum value at small |J0| (J0 is the exchange interaction at a distance of the closest approach),and levels off at large |J0|, whereas in the LJ fluids it increases in the region of large |J0| and reaches a second maximum.At low temperatures, m, which is defined as the exponent in the form of PRPM ∝ Qabm, approaches 0 in the LJ fluids in the region of |J0| = 1011—1012 s-1.The calculated results are compared with the experimental results obtained for 1-hydroxy-1-methylethyl radicals in 2-propanol.The main features of the experimental observations are qualitatively better explained by the present models of the LJ fluids than by the continuum with |J0| = 1011—1012 s-1.These results are ascribed to the effect of the solvent structure which tends to keep the solvent-separated radical pair for a longer time.