The image luminescence spectrum of image in image2GeF6 crystals—A quantum chemical study

The image emission spectrum of Cs2GeF6:U4+ single crystals has been calculated using the relativistic ab initio model potential (AIMP) embedded cluster method. It consists of a series of broad, intense bands in the UV followed by broad and increasingly weaker bands in the visible and near infrared spectral range, which appear to be associated with emissions from the lowest image excited state, image, to a number of levels of the image manifold. The electric dipole allowed emission of highest energy, image, is found to have very low oscillator strength, image; this value is only 4% of the most intense electronic transition: image whose electronic origin is found to be at image. A very large Stokes shift of image is obtained, which should result in low luminescence quenching due to reabsorption and should favourably contribute to the emission quantum efficiency. The lifetime of the spontaneous emission from image has been calculated to be in the nanoseconds range: 33 ns.