| 摘要 |
A green diamond characterized in that the nitrogen content in crystals is 5 x 10<1><6> - 3 x 10<1><9> atoms/cm<3>, the absorption coefficient of H2 centers at a wavelength of 800 nm is 0.3 - 6 cm<-><1>, the absorption coefficient of the Ib type nitrogen at a wavelength of 500 nm is 0.05 - 1.5 cm<-><1>, and the absorption coefficients of H3 centers, H4 centers, N-V centers and GR1 centers in the visible region are not more than 0.2 cm<-><1>. The production of such a green diamond comprises the steps of preparing a clear-yellow Ib type diamond whose nitrogen in crystals is 5 x 10<1><6> - 3 x 10<1><9> atoms/cm<3>, irradiating this diamond with an electron beam having not less than 1 x 10<1><8> electrons/cm<2> at an accelerating voltage of 2 - 4 MeV, and subjecting this diamond to a heat treatment at a temperature of 1500 DEG C - 1800 DEG C in a vacuum of not more than 10<-><3> torr, or at a temperature of not less than 1600 DEG C under a pressure of not less than 3.0 GPa. |
