The Nature of the Self-Luminescence Observed from Borosilicate Glass Doped with Es

We have been conducting spectroscopic investigations of transuranium elements in silicate matrices. Glasses doped with Es show a blue self-luminescence (SL) band having a maximum at ∼455 nm, and minor bands at 650 and 730 nm. With time, the intensity of the 455 nm band decreases, whereas the 650 and 730 nm bands increase. These SL bands are believed to arise from defect centers that are produced by alpha-particles and recoiling atoms. The band at 455 nm is assigned to originate from oxygen defect centers within the Si-O-Si network, whereas the bands at 650 and 730 nm are believed to originate from non-bonding oxygen hole centers (NBOHC), and Si-micro cluster sites, respectively. The latter two bands (650 and 730 nm) were also observed in the photo-luminescence(PL) spectra obtained with a 488 nm excitation. However, the PL profile showed a dependence on the power of the excitation flux. The 730 nm band dominates at low power, while at higher levels this band's intensity was "quenched" relative to the 650 nm emission. A new band also emerges, concomitantly, around 770 nm on freshly prepared samples and becomes dominant at laser powers greater than 1W. Details of these investigations are discussed in this paper.