New trapped-electron and trapped-hole centres in X-rayed KCl:Tl⁺ crystals

Abstract

The optical absorption spectra of KC1 crystals containing TI+ ions have been investigated. After X-ray irradiation at 300 K two absorption bands are observed at 228 and 280 nm at 77 K whichdo not arise from the same centres. A correlation among the 228 nm. 280 nm. and F bands is found during the optical or thermal excitation of the X-rayed crystals. The 228 nm band is assigned to a trapped-hole centre, namely V2 centre closely associated with TIt. while the 280 nrn hand is assigned to a trapped-electron centre, TI-. On a etudik le spectre d'absorption optique de crist;~ux de KC1 contenant des ions TI+. Apres irradiation aux rayons X I 1 300 K, on a observC i 228 et 280 nm h 77 K , deux bandes d'absorption qui ne proviennent pas des memes centres. On trouve une corl.Clation entre les bandes i 228 nm, la bande 280 nrn et la bande F durant I'excitation optique ou therrnique des cristnux il-radies ;tux rayons X. La bande h 228 nm est attribuCe B un centre i trou piCge. c'est-i-dire un centre V2 Ctroitement associke 1 TI+. alors que la bande : I 280 nm est attribuee h un centre ,;I electron piege, TI-. Can. J . Phys.. 57. 1510(1979) [Tnduit par le journal] Can. J. Phys. Downloaded from www.nrcresearchpress.com by University of P.E.I. on 11/18/14 For personal use only.

Electrolytic reduction of Tl+ ions in KCl crystals

“…Absorption bands at 640 and 380 nm due to Tl 0 [11] are not observed in the present study. Therefore it is suggested that not Tl 0 but Tl À is created by the electrolytic coloration.…”

“…Tl 0 is created by trapping of electron at Tl + under X-ray irradiation at 77 K, but it is not stable at 290 K [10,11]. Absorption bands at 640 and 380 nm due to Tl 0 [11] are not observed in the present study.…”

Tin nanoclusters obtained in potassium chloride by thermal annealing

“…The methods for obtaining such negative metal ions were various, starting with X-ray irradiation, additive or electrolytic coloration. So far, was demonstrated the existence of Pb - [2], Ag - [3], Cu - [4], Tl - [5] and even Sn - [6]. The change of the valence for heavy metal ions were also observed in CaF 2 : Pb 2+ crystals under X-ray irradiation at the temperatures over 300 K, where Pb 2+ ions are transformed into Pb + , Pb + -Pb 2+ and/or Pb 0 (2) centres [7].…”