Abstract
ENDOR-measurements of the photo-excited triplet state of naphthalene, 1-monodeutero-naphthalene and 1,4-dideutero-naphthalene in durene at 4.2°K are reported. The hyperfine interaction constants of α- and β-protons and α-deuterons, the corresponding spin densities and the axis of the hyperfine tensor are determined. A doublet splitting of all ENDOR lines indicates the existence of four (instead of two) inequivalent sites for naphthalene molecules in the durene matrix.