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

Abstract

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 T1, Exc is measured at 300 °K and 77 °K and at Larmor frequencies between 0.4 and 44 MHz. From the frequency dependence of T1, Exc the exciton-proton correlation time τc 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.