Vibrational and electronic spectra of

Abstract

Single crystals of doped with molar concentrations of between 0.1 and 20% have been synthesized by the hydrothermal method, and studied by absorption, excitation and luminescence spectroscopy at temperatures down to 4 K. The observed spectral features were consistently assigned with reference to those of the corresponding europium hexachloroelpasolite. No distortion from octahedral symmetry was evident for the site in the 0.1 mol%-doped crystal, but small splittings of magnetic dipole zero-phonon lines in the spectra of the 20%-doped crystals are observed below 20 K. The vibrational behaviour of has been interpreted, and the energy-level scheme of the ion was deduced from the observed and inferred zero-phonon-line positions in the optical spectra. A parametrized Hamiltonian was fitted to 21 crystal-field levels of in . The fourth- and sixth-degree crystal-field parameters were about 1.6 times larger than for . The temperature shifts of the crystal-field levels were found to be negative, in contrast to the mostly positive shifts previously reported for actinide systems in octahedral symmetry, and were largely determined by the changes in the Slater parameters rather than the crystal-field parameters. A preliminary study has been made of the decay kinetics of the levels. is quenched by a cross-relaxation mechanism, and also by a thermally activated mechanism. The lifetime of does not exhibit a noticeable temperature or concentration dependence.

Effects of Cr3+ concentration on the optical properties of Cs2NaAlF6 single crystals

“…The samples used in this work were grown by hydrothermal method [14,32]. Single crystals of Cs 2 NaAl 1À x Cr x F 6 with the nominal concentrations x¼0.001, 0.01, 0.03, 0.1, 0.3 and 0.5 were prepared.…”

Emission spectra of lanthanide ions in hexafluoroelpasolite lattices excited by synchrotron radiation

“…In the present study, the emission spectra of the tripositive ions of Sm, Gd, Tb, Ho, and Er excited by synchrotron radiation at $10 K are presented and detailed interpretations are provided where possible. There have been some previous 4f N -4f N emission results reported for hexafluoroelpasolite systems comprising Nd 3+ [3], Eu 3+ [4], Tb 3+ [5,6], Er 3+ [7], Tm 3+ [8], and Yb 3+ [9], and experimental results and/or theoretical simulations of 4f N M 4f NÀ1 5d spectra were reported for Ce 3+ [10,11], Pr 3+ [12], Nd 3+ [3], Er 3+ [13], and Tm 3+ [13,14]. [4].…”

“…Fluoride crystal hosts possess greater thermal stability and relative inertness compared to other halide hosts, and lower synthesis temperatures and higher band gap energies compared to oxide hosts. The most popular fluoride crystal hosts that have been extensively investigated are MYF 4 (M = Li, Na) and MF 2 (M = Ca, Sr). In the former (M = Li), the Ln 3+ ions are situated at S 4 site symmetry, whereas in the alkali metal fluorides there are several available sites due to charge incompatibility.…”

Vacuum ultraviolet excitation spectra of lanthanide-doped hexafluoroelpasolites

“…The magnetic properties [87], vibrational spectra [88] and intraconfigurational 4f N -4f N spectra of Nd 3+ [89], Eu 3+ [90,91], Tb 3+ [92], Er 3+ [93], Tm 3+ [94] and Yb 3+ [95,96] [3,101]) although a spectral interpretation was not given [3,99]. The 4f N -4f N −1 5d spectra of Nd 3+ [89], Er 3+ [102] and Tm 3+ [102,103] in the Cs 2 NaYF 6 host have been previously reported and are subsequently referred to with respect to the spectra obtained herein.…”