Аннотация:The effect of isotopic modification of diamond lattice on photoluminescence (PL) and optical absorption spectra of ensembles of SiV- centers was studied. Thin epitaxial diamond layers were grown by a microwave plasma CH4/H-2 mixtures using methane enriched to 99.96% for either C-12 or C-13 isotopes, while the Si doping was performed by adding a small percentage of silane SiH4 into the plasma. Temperature dependent SiV- ZPL spectra in absorption were measured at 3-80K to monitor the evolution of the ZPL fine structure. It is found that the SiV- ZPL at 736.9nm observed in PL for C-12 diamond at T=5K, exhibits a blue shift of 1.78meV, to 736.1nm in C-13 diamond matrix. Narrow ZPL with the width (FWHM) of 0.09meV (21GHz) was measured in absorption spectra at T=3-30K in the Si-doped C-13 diamond. Besides the charged SiV- center, the absorption of the neutral SiV0 defect at 946nm wavelength has also been detected. From changes observed in SiV- phonon band structure in PL with isotopic modification, the band at 64meV was confirmed to be a local vibration mode (LVM) involving a Si atom.