Uniaxial stress measurements on optical transitions in yellow-luminescing brown diamonds

Abstract

The authors report the effect of uniaxial stress perturbations on seven independent zero-phonon luminescence lines frequently observed in a hitherto largely ignored class of diamonds: brown diamonds that emit yellow luminescence under 365 nm excitation. The lines are assigned as follows: the 3.204 eV line to an A (excited) to E (ground) transition at a trigonal centre; 2.721 and 3.224 eV lines to monoclinic I centres; 2.649, 2.699 and 2.748 eV lines to rhombic I centres; and the 2.478 eV line possibly to a triclinic centre. On comparing their phonon sidebands, symmetries, responses to stress and zero-phonon energies, the authors suggest that the 2.649, 2.699, 2.748 and 2.721 eV lines occur at closely related centres, as do the 3.204 and 3.224 eV lines.