PRESSURE-TUNING FT-RAMAN SPECTROSCOPIC STUDY OF THE T-2G PHONON MODE OF A DIAMOND-ANVIL CELL

The stress behaviour of a type-IIA diamond in a commercial diamond-anv il eel has been examined by measuring the position of the T-2g phonon mode of the top diamond in the cell (originally located at similar to 1332 cm(-1)) during a pressure-tuning FT-Raman microspectroscopic stud y at various pressures throughout the 0.001-62.2 kbar range. In genera l, the components of the scattered Raman signal from different depths appear as discrete band envelopes rather than a continuous gradient th roughout the depth of the diamond. The changes taking place in the ban d structure with the variation in depth indicate the occurrence not of phase changes but of discontinuities in the pressure gradient through out the diamond. For measurements made at the bottom edge of the diamo nd (i.e. at the sample-diamond interface), there is a linear relations hip between the position (v, wavenumbers) of the T-2g phonon mode and the pressure (P, kbar) such that dv/dP = 0.16 cm(-1) kbar(-1). (C) 199 7 Elsevier Science B.V.