Protonen-Relaxation durch Triplett-Excitonen in Naphthalin-und Anthracen-Kristallen

Abstract

The spin lattice relaxation time T₁ of protons in naphthalene and anthracene crystals is decreased by the presence of metastable triplet excitons in these crystals. The exciton induced relaxation time T_{1, Exc} is measured at 300 °K and 77 °K and at Larmor frequencies between 0.4 and 44 MHz. From the frequency dependence of T_{1, Exc} the exciton-proton correlation time τ_c at the two temperatures is determined to 5.5 · 10 ^-12 sec and 4.1·10 ^-12 sec (±10%) in anthracene and 2.1·10^-11 sec and 1·10 ^-11 sec in naphthalene, assuming scalar proton-electron interaction and statistical incoherent hopping motion of the excitons. The predictions of a theoretical model for exciton-migration are in satisfying agreement with the experimental results as far as experimental data for the parameters of that model are available.