Interstitial bismuth dimers and single atoms as possible centres of   broadband near-IR luminescence in bismuth-doped glasses
  Absorption, luminescence and Raman spectra of interstitial bismuth atoms, $\mathrm{Bi}^{0}$, and negatively charged dimers, $\mathrm{Bi}^{2-}$, in alumosilicate, germanosilicate, phosphosilicate and phosphogermanate glasses networks are calculated by time-dependent density functional method. On grounds of this calculation an extension of our previously suggested model of broadband near-IR luminescence in bismuth-doped glasses is put forward. 
V.O.Sokolov, V.G.Plotnichenko, E.M.Dianov
cond-mat.mtrl-sci