Absorption spectra of hydrogen in C-13 diamond produced by high-pressure, high-temperature synthesis

Sharp absorption lines produced by hydrogen in diamond have been studied in diamonds grown from C-13 by high-pressure, high-temperature synthesis. Analyses of the two-phonon intrinsic absorption and of the Raman shift have shown that the C-12 content of the diamond is 13.5%. This value is entirely consistent with the relative intensities of the absorption lines at 3107 and 3098 cm(-1), confirming that they are due to a strongly localized C-H stretching vibration. A correlated line, observed at 1405 cm(-1) for natural diamond, and attributed to the C-H bending vibration, exhibits both an isotope shift and a shift due to weak coupling with the one-phonon modes. By analogy with natural diamond, lines for the C-13 diamond at 2757 and 4469 cm(-1) are assigned to the combinations 2 (h) over bar omega(b) and (h) over bar omega(s) + (h) over bar omega(b), respectively, where (h) over bar omega(s) and (h) over bar omega(b) are the stretch and bend frequencies. The frequency invariance, on carbon isotope substitution, of a hydrogen-related line at 3237 cm(-1) is not inconsistent with the proposal that this is produced by a N-H vibration.