Diffusion processes involved in the exothermic triplet–triplet energy transfer in n-hexane at high pressure: evaluation of diffusion coefficients of benzophenone, triphenylene and naphthalene

By using the exothermic energy transfer previously determined as a function of pressure, the rate constant for diffusion, kdiff, was evaluated for benzophenone triplet (3BZP∗)/naphthalene (N), triphenylene triplet (3TPH∗)/N and triphenylene singlet (1TPH∗)/BZP, and the diffusion coefficients, Di, for BZP, TPH and N were determined in n-hexane at pressures up to 400 MPa by assuming that Di for the excited states is equal to that for the ground state. The diffusion coefficients evaluated agreed well with the available data at 0.1 MPa. The quenching rate constants, kq, for 1TPH∗/O2 and 1TPH∗/CBr4 were also measured at pressures up to 400 MPa in this work. For these systems, the values of kdiff were also evaluated and compared with those calculated by coupling Di for TPH in this work with that for the quenchers determined by the dynamic fluorescence quenching in the previous works.