Spin-spin and spin-lattice relaxation in the triplet state of AB-pairs in isotopically mixed crystals of naphthalene

Abstract

Electron spin echo techniques in combination with laser flash excitation have been used to study the spin relaxation processes in the triplet state of inequivalent naphthalene dimers in zero field down to 0·35 K. The spin-spin relaxation is dominated by a fast spin-lattice relaxation induced by a thermally activated exchange process between the two Davydov components. The technique allows us to obtain selectively S ₁ ← S ₀ excitation spectra which show that energy transfer is slow compared to the spin relaxation rates.