ESR-Untersuchungen an Naphthalin-d₈: Naphthalin-h₈-Mischkristallen in deren Triplett-Zustand

Mixed crystals of perdeuterated naphthalene (N-d8) and normal naphthalene (N-h8) were investigated by epr-absorption during the UV-irradiation at 4.2°K. Besides the well-known epr-lines of the isolated N-h8 molecules in their lowest triplet state one observes in this isotopically dilute system new epr-lines. We call them M-lines. They are due to pairs of N-h8 molecules as nearest neighbours. Caused by exchange interaction the triplet excitation oscillates quickly between the two molecules. The triplet exchange energy of two nearest neighboured N-h8 molecules within the unit cell is found from the line width of the M-lines to be J/hc - (5±0.7) cm−1. Furthermore one observes epr-lines of N-h8 trimers in teh triplet state. Preliminary results are reported concerning the concentration dependence of the relaxation and of the lifetime of the metastable triplet state.