Nd3+ Ion as a Structural Probe in Studies of Selected Oxide Host Lattices: Coupling the Low-Temperature High-Resolution Spectroscopic Techniques with Microscopy

Combining XRD and SEM techniques with site selective spectroscopy for structural and spectroscopic studies of Nd3+-doped LuPO4 micro-powders

Site selective high resolution laser spectroscopy of europium in calcium binding proteins

Radiative transition properties of Yb3+ in Er3+/Yb3+ co-doped NaYF4 phosphor

Site-selective laser spectroscopy and defect configurations of the Nd3+-Li+ centres in ZnO powders

High pressure solid state chemistry defect dynamics using site selective laser spectroscopy

Site-selective spectroscopy of the uranyl ion in borosilicate glass

Site-selective laser spectroscopy of lanthanide-binding sites in calmodulin

We have developed a site-selective laser method to study the aggregation kinetics of defect sites as a result of heat treatment in ${\mathrm{EuF}}_{3}$-doped ${\mathrm{CaF}}_{2}$ crystals. The crystals contain ${\mathrm{Eu}}^{3+}$ in four dominant defect sites and one minor site that differ in the number of nearby dopant and fluoride interstitial ions. A nonequilibrium site distribution was created by quenching the high-temperature distribution. The kinetics of the reequilibration to a lower-temperature distribution was followed by measuring the absolute concentrations of the defect sites with site-selective laser spectroscopy. The functionality of the temporal changes, the absolute concentrations, and the concentration and temperature dependence of the rate constants have been used to definitively identify the four major sites and to quantitatively describe the entire behavior of the defect distributions. The four sites are identified as an isolated ${\mathrm{Eu}}^{3+}$; a single-pair site of a ${\mathrm{Eu}}^{3+}$ ion and a compensating fluoride interstitial; a dimer consisting of two ${\mathrm{Eu}}^{3+}$ ions, no fluoride vacancies, two displaced fluoride ions, and three fluoride interstitials (2\ensuremath{\Vert}0\ensuremath{\Vert}2\ensuremath{\Vert}${3}_{1}$); and a trimer of three ${\mathrm{Eu}}^{3+}$ ions and four fluoride interstitials (3\ensuremath{\Vert}0\ensuremath{\Vert}2\ensuremath{\Vert}${4}_{1}$). It is suggested that the trimer and dimer are related to the hexamer clusters observed with heavier rare-earth dopants and that the hexamers contain extra fluoride interstitials that form a series of clusters with the largest possible cluster being 6\ensuremath{\Vert}0\ensuremath{\Vert}32\ensuremath{\Vert}12. We also determined activation energies of 0.49\ifmmode\pm\else\textpm\fi{}0.08 eV and 1.5\ifmmode\pm\else\textpm\fi{}0.4 eV for the formation of the dimer and trimer, respectively. This work presents the first complete microscopic picture for the solid-state defect chemistry of a fluorite material. It is in agreement with recent predictions of hades (Harwell Automatic Defect Examination System) models for fluorite defect centers.

Lanthanide ions are generally known to possess narrow 4fn to 4fn transitions in both excitation and fluorescence that are sensitive to the coordination environment surrounding the ion. Selective excitation with a narrowband laser can spectrally discriminate one lanthanide ion environment from another based upon differences in the crystal fields associated with the unique lanthanide ion sites. This paper describes site selective laser spectroscopic experiments where europium ions have been coordinated to proteins in sites normally occuppied by calcium ions.

Investigation of photoluminescence properties of Eu3+-doped GdAlO3 and LaAlO3 by site-selective laser spectroscopy

Defect dynamics measured with diamond anvil cell and site-selective laser spectroscopy

The individual Er3+ sites in CdF2:Er3+ are determined by site selective laser spectroscopy and are monitored as the crystal is changed from the insulating to the semiconducting state. The site distribution is controlled by clustering of the Er3+ dopant ions and their charge compensating fluoride interstitials (F′i). Simple, single pair sites where an Er3+ ion is locally compensated by a Fi are found to have minor importance in contrast with other fluorites. The conversion to a semiconductor state results from oxidation of the F′i that locally compensate the Er3+ clusters. No new sites are observed that arise from local compensation by electrons. Differences in the oxidation potential between the various clusters suggest differences in the numbers of Fi associated with each cluster. It is suggested that the changes in the site distribution that occur for dopants with different ionic radii account for the inability of some dopants like La3+, Ce3+, and Pr3+ to produce the semiconducting state. The observation of the dominance of clustering in CdF2 lends support to previous interpretations of the activation energies for electron transport.

Site selective laser spectroscopy study of defect equilibria in MgO:Cr 3+

Site selective laser spectroscopy has been used to identify the defect sites in PbF2:Er3+ and follow their distribution as a function of dopant concentration and annealing temperature. Three sites labeled S1, S2, and S3 are found to correspond to single Er3+ ions with nearby F′i charge compensation, three sites labeled D1, D2, and D3 are found to correspond to clusters (dimer or higher) of Er3+ ions with nearby F′i charge compensation, and a cubic site labeled C where the Er3+ ion is compensated distantly. The cubic site is found to continually increase relative to S1 as the Er3+ concentration is raised. This behavior is contrary to that expected from simple mass action relationships, but is similar to that found in other fluorites. As the annealing temperature is raised, the cubic site increases markedly while the other sites decrease markedly over a small temperature range around the superionic transition temperature. This change is direct evidence for the sudden increase in charge screening effects which have been suggested as the driving force for the transition. It is suggested that the additional interactions caused by strain fields exaggerate the Debye–Hückel nonideality corrections and make the screening effects more effective.

We report here on the electronic structures of [(Mo6Cl8)Cl6]2− and [(Re6S8)Cl6]4− obtained by the Tamm–Dankoff configuration interaction approximation, where Darwin and mass-velocity terms are taken into account through the model core potentials, and the spin–orbit interaction term is included in a semiempirical manner. These complexes have absorption spectra ranging from the visible to the near-ultraviolet energy region and have the long-lived luminescence. The calculated results of the transition moments roughly reproduce the experimental absorption and emission spectra. Especially for the absorption spectra, the theoretical strong intensity for the region higher than 4.5 eV in the two complexes is in good agreement with the experimental results. The obtained intense peak at 3.9 eV may correspond to the experimental broad peak at approximately 3.6 eV for the Mo complex. For the Re complex, the calculated intensity distribution gives one broad peak at around 3.1 eV. This peak may correspond to the experimental peak at 2.9 eV. In the experimental emission spectra, the maxima are located at 1.62 eV for the Mo complex and approximately 1.8 eV for the Re complex. Theoretically, 12 and eight states are found in the energy range between 1.5 and 2.0 eV for the Mo and Re complexes, respectively. At least one, if not more, of these states would be responsible for each emission maximum. To determine the character of the above transitions, the absorption and emission transitions were experimentally shown to be ligand-to-metal charge-transfer transitions and metal-localized transitions, respectively. Theoretically, absorption transitions were characterized as a mixture of metal-localized transitions and ligand-to-metal charge-transfer transitions, and emission transitions a mixture of metal-localized transitions and metal-to-ligand charge-transfer transitions.