Isotope shifts of nitrogen-related localised mode vibrations in diamond

Abstract

Cathodoluminescence studies of the 3.188 eV vibronic band in ¹²C and ¹³C synthetic diamonds show that the sharp peaks at around 3.0 eV are local-mode replicas of the zero-phonon line. Accurate measurement of the isotope shifts shows that one of these modes involves the vibration of a single nitrogen atom. This interpretation is confirmed by measurements on ¹⁵N-doped synthetic diamond. A vibrational absorption peak at 1856 cm^-1, superimposed on the tail of the two-phonon lattice band, is shown, from vacancy-enhanced aggregation studies on ¹⁵N-doped diamond, to be a di-nitrogen centre.