LOCALIZED VIBRATIONAL-MODES IN DIAMONDS GROWN FROM MIXED CARBON ISOTOPES

Localised vibrational modes associated with the 5RL, 3.188 eV and 2.807 eV cathodoluminescence systems, the local mode peak in the H2 absorption band and the local mode absorption peak at 1344 cm-1 in type Ib diamond have been studied in synthetic diamonds grown from 60% C-12 and 40% C-13. The results show that the 5RL system is produced by transitions at a [100] split-interstitial, that the 3.188 eV and 2.807 eV centres both incorporate a single nitrogen atom and more than one carbon interstitial and that the 1344 cm-1 peak appears to be associated with the vibration of a unique carbon atom. The data also demonstrate that the simple analysis which satisfactorily accounts for the energies and intensities of components in very localised modes is inadequate to interpret the behaviour of modes which are only just localised.