Luminescence of negatively charged single vacancies in diamond: ND1 center

Strong photoluminescence (PL) of ND1 radiation center with zero-phonon line (ZPL) at 393.5 nm has been excited in irradiated diamonds with a laser working at a wavelength of 355 nm. Emission of the ND1 center consists of ZPL and vibrational replicas related to quasilocal vibrations of an energy 76 meV. PL and absorption spectra of ND1 center exhibit very close mirror symmetry. The energies of the quasilocal vibrations are the same in luminescence and absorption. The interaction with the lattice phonons at the ND1 center is very weak. In luminescence of the irradiated diamonds, ND1 center behaves like one related to simple primary radiation defects in negative charge state. PL of the ND1 center is stimulated by nitrogen donors and suppressed by boron acceptors. It is assumed that the luminescence of the ND1 center is effectively excited only in the spectral range of its intrinsic absorption from 340 to 390 nm.