Analysis of the Absorption and Emission Spectra of U³⁺ in CsCdBr₃ Single Crystal

Abstract

Laser selective excitation and emission spectra as well as σ- and π-polarized absorption spectra have been recorded for U3+ ions diluted in a CsCdBr3 host crystal. Three distinct U3+ sites were observed. For the principal site, which was attributed to a symmetric dimer center, 45 crystal-field energy levels in the 0−13250 cm-1 energy range were assigned. These experimentally determined levels were fitted to thirteen parameters of a semiempirical Hamiltonian representing the combined atomic, one-electron crystal field as well as two-particle correlation crystal-field (CCF) operators, with an rms deviation of 41 cm-1. Above 14000 cm-1 strong electric-dipole allowed 5f3−5f26d transitions were observed. The lifetime of the 4G7/2 fluorescing level has been measured for each of the three U3+ sites at liquid-helium temperatures and are 2.5, 4.3, and 7.6 μs. The emission is strongly influenced by temperature due to strong phonon coupling of the 5f3 states with the nearby 5f6d1 states. Visible upconversion fluorescence observed when pumping the 4I9/2 − (4F7/2 + 4I15/2) absorption transitions of the principal site A is attributed to excited-state absorption (ESA).

Optical Spectra and Energy Levels Analysis of the 4fNIons Doped into Ba2YCl7

“…The consecutive ( i = 1–4) sidebands are coupled to the lines at 20 536 cm –1 (ν i ) and 20 483 cm –1 (ν i ′) of electronic origin and are shifted with respect to these lines by 57 ( i = 1), 99 ( i = 2), 203 ( i = 3), and 256 ( i = 4). The energies of ν 3 and ν 4 vibronic sidebands correspond exactly to those observed also in Ba 2 YCl 7 crystals doped with U 3+ and U 4+ ions …”

“…The energies of ν 3 and ν 4 vibronic sidebands correspond exactly to those observed also in Ba 2 YCl 7 crystals doped with U 3+ and U 4+ ions. 20 The combined analysis of the 77 K emission and excitation spectra (Figures 2 and 3) has enabled identification of 66 energy levels for Ba 2 YCl 7 :Pr 3+ , which were subsequently included in the fittings (section 5). Comparison of the experimental and calculated energy levels reveals that only the multiplets 1 G 4 and 1 S 0 have not been experimentally observed, probably due to the equipment limitations.…”

Electronic Structure of U3+in Cs3Lu2Cl9and Cs3Y2I9Single Crystals

“…In recent years, a number of crystal-field analyses of U 3+ ions in polycrystalline samples and single host crystals have been reported. − Since LaCl 3 (refs and ), LiYF 4 (ref ), and Cs 2 MYX 6 (where M = Li or Na and X = Cl or Br) 9,10 were the only host crystals in which the uranium ions were located at a site symmetry higher than C 2 v , we turned our attention toward high-symmetry hosts. Recently, we have completed an analysis on optical spectra and crystal-field (CF) calculations of U 3+ -doped CsCdBr 3 single crystals . The uranium ions incorporated in this host crystal possess C 3 v site symmetry.…”

“…In this paper, the results of our spectroscopic investigations on U 3+ -doped Cs 3 Lu 2 Cl 9 and Cs 3 Y 2 I 9 single crystals are presented. Due to a similar surrounding of the U 3+ ions, these host crystals together with those of CsCdBr 3 (ref ) and Cs 2 NaYX 6 (X = Cl or Br) 9,10 are suitable for comparison purposes on the influence of the descending site symmetry on the structure of the crystal-field levels. Besides, with the variation of the environment from chloride to iodide ligands, some trends in the energy level structure of the 5f 3 and 5f 2 6d 1 configuration could be investigated.…”

Personal recollections of interactions with Bill Carnall

“…This paper paved the way for further studies, though it would be an additional 15 years until such analyses were undertaken [4,5]. Recently [6], we revised and completed this paper and also expanded the investigations on, among others, laser selective excitation and emission spectra of U 3+ ions doped in various host crystals with a very high [7,8] or very low [9,10] site symmetry of the ion, as well as on host crystals doped with two different ions [11]. I would like to emphasize here that from among a very large number of Bill Carnall's papers I have shown the enormous scientific importance and inspiring influence of only two of them.…”