Raman spectroscopy of isotopically pure (12C, 13C) and isotopically mixed (12.5C) diamond single crystals at ultrahigh pressures

• Published in: Journal of experimental and theoretical physics 2016-09, Vol.123 (3), p.443-451
• Main Authors: Enkovich, P. V., Brazhkin, V. V., Lyapin, S. G., Novikov, A. P., Kanda, H., Stishov, S. M.
• Format: Article
• Language: English
• Subjects: ACCURACY; CARBON 12; CARBON 13; CARBON ISOTOPES; Classical and Quantum Gravitation; COMPRESSION; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIAMONDS; EFFECTIVE MASS; Elementary Particles; HELIUM; HYDROSTATICS; MONOCRYSTALS; Particle and Nuclear Physics; PHYSICAL PROPERTIES; Physics; Physics and Astronomy; PRESSURE RANGE GIGA PA; Quantum Field Theory; RAMAN EFFECT; Raman spectra; RAMAN SPECTROSCOPY; Relativity Theory; Solid State Physics; Solids and Liquids
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776116070049

The Raman scattering by isotopically pure 12 C and 13 C diamond single crystals and by isotopically mixed 12.5 C diamond single crystals is studied at a high accuracy. The studies are performed over a wide pressure range up to 73 GPa using helium as a hydrostatic pressure-transferring medium. It is found that the quantum effects, which determine the difference between the ratio of the Raman scattering frequencies in the 12 C and 13 C diamonds and the classical ratio (1.0408), increase to 30 GPa and then decrease. Thus, inversion in the sign of the quantum contribution to the physical properties of diamond during compression is detected. Our data suggest that the maximum possible difference between the bulk moduli of the 12 C and 13 C diamonds is 0.15%. The investigation of the isotopically mixed 12.5 C diamond shows that the effective mass, which determines the Raman frequency, decreases during compression from 12.38 au at normal pressure to 12.33 au at 73 GPa.