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.