Gary W. Burdick

A new contribution to spin‐forbidden rare earth optical transition intensities: Gd3+ and Eu3+

Quantitative calculations show that numerous spin‐forbidden linear optical transitions observed in trivalent rare earth ions acquire a major fraction of their intensity from hitherto neglected contributions involving spin–orbit linkages within excited configurations. Motivated by the importance of analogous linkages previously demonstrated in two‐photon absorption, we derive a general expression applicable for all lN→lN transitions which can be incorporated into a revised Judd–Ofelt analysis of observed intensities. Presenting this revised analysis of observed linear absorption intensities for Gd3+ and Eu3+, we show that the new contribution is often comparable to standard contributions. With substantial modification of previously fitted phenomenological parameters, an improved fit to observed intensities is achieved, suggesting that reanalysis of linear intensity data for all trivalent rare earths is warranted.

Electronic absorption spectra, optical line strengths, and crystal-field energy-level structure of Nd3+ in hexagonal [Nd(H2O)9](CF3SO3)3

Abstract Optical absorption measurements are used to locate and assign 79 crystal-field (Stark) levels split out of the 4f 3 electronic configuration of Nd 3+ in single crystals of neodymium nonahydrate tris(trifluoromethanesulfonate), [Nd(H 2 O) 9 ](CF 3 SO 3 ) 3 , denoted hereafter as NdTRF. Line strengths are determined for 56 transitions between Stark levels. Single crystals of NdTRF have hexagonal, P6 3 /m(C 6h 2 ) space-group symmetry, and each Nd 3+ ion is coordinated to nine water molecules in a slightly distorted tri-capped trigonal prism structure of C 3h symmetry. The energy-level structure of 4f 3 (Nd 3+ ) in NdTRF is analyzed in terms of a model Hamiltonian that includes consideration of both one-electron crystal-field and two-electron correlation-crystal-field interactions, the latter interactions making important contributions to the energy-level structures of several 4f 3 [ SL ] J multiplet manifolds. Line strength data obtaibned for NdTRF is analyzed in terms of a general 4f → 4f transition intensity model in which the details of the 4f-electron/crystal-field/electric-dipolar radiation-field interactions are represented in parametric form. The derived parameters provide information about structural properties and interaction mechanisms that contribute to 4f → 4f transition intensities. The general crystal-field and intensity parameters are further analyzed in terms of a set of ‘intrinsic’ parameters that are related to contributions from individual Nd 3+ OH 2 pairwise interactions.

Crystal field parametrizations for low symmetry systems

For lanthanide ions in sites with no axis of symmetry (C1 or Ci symmetry) there is no obvious choice for the quantization axis. In these cases, the orientation of the lanthanide site may be rotated by three arbitrary Euler angles ϕ1 , θ, and ϕ2 , where ϕ1 and θ determine the orientation of the z axis, and ϕ2 determines the orientation of the crystal about the z axis. We show that appropriate selection of these three Euler angles allows the number of independent crystal-field parameters to be reduced from 27 to 24. This paper explores the possible ways of performing this parameter reduction, and presents the relationship between the different sets of resulting crystal-field parameters.

A new contribution to spin‐forbidden rare earth optical transition intensities: Analysis of all trivalent lanthanides

We expand upon recent quantitative calculations which show that numerous parity‐ and spin‐forbidden linear optical transitions observed in trivalent rare earth ions acquire a major fraction of their intensity from hitherto neglected contributions involving spin–orbit linkages within excited configurations. Extending our revised analysis of observed linear absorption intensities for Gd3+ and Eu3+ to the other nine trivalent lanthanides with visible wavelength transitions, we find that the new contributions are at least as important in these other lanthanides, and are often comparable to standard contributions. We also show that spin‐forbidden ΔS=1 transitions are selectively modified over the spin‐allowed ΔS=0 transitions. In addition, we examine contributions from linkages with g orbital excited states in the light of recent electronic Raman scattering data for lanthanide phosphates, and show that these long neglected terms may actualy dominate the transition intensity. With substantial modification of pr...

Luminescence spectroscopy of high-energy 4f11 levels of Er3+ in fluorides

The 4f11 energy levels of Er3+ in LiYF4 in the spectral region 39000–65000 cm−1 have been studied. The agreement between experimental energy levels, obtained from luminescence excitation spectra, and calculated energy levels is good. Luminescence originating from high-lying energy levels has been investigated. Emission from the states 4D1/2 (∼47 200cm−1), 2F(2)7/2 (∼54700cm−1) and 2F(2)5/2 (∼63 300cm−1) is observed. 2F(2)5/2 emission occurs for Er3+ in LaF3, where the 2F(2)5/2 level is situated just below the lowest 4f105d state, but also for Er3+ in LiYF4, where it lies in between the two lowest 4f105d states.

Analyses of 4f11 Energy Levels and Transition Intensities Between Stark Levels of Er3+ in Y3Al5O12

ABSTRACT Absorption and fluorescence spectra obtained at temperatures as low as 4 K were investigated between 200 and 1550 nm on samples containing approximately 1.2 at. wt. % Er in Y3Al5O12 (YAG). Within this wavelength range 125 experimental energy (Stark) levels were analyzed, representing data that span 29 2S+1 L J multiplet manifolds of Er3+(4f11) in D2 sites up to an energy of 44,000 cm−1. Agreement between calculated and observed Stark levels was achieved with an r.m.s. deviation of 11.2 cm−1. These transitions originate from the ground-state Stark level in the 4I15/2 manifold to J + 1/2 Stark levels associated with each of the 28 excited-state manifolds. A total of 88 ground-state absorption transition line strengths were measured for 19 2S+1 L J multiplet manifolds between 280 and 1550 nm. For line strength measurements, the Er3+ ion is assumed to be distributed homogeneously throughout the D2 cation sites of Y3+ in the lattice. The line strengths were analyzed with a weighted (E i − C i )/E i , with an r.m.s. error of 0.25. Use of a “vector crystal field” parametrization resolves ambiguities in the transition intensity parameters and allows for the definition of polarization-resolved Judd-Ofelt parameters, which may have wide-ranging applicability for future Judd-Ofelt-type intensity calculations.

Analyses of the ultraviolet spectra of Er3+ in Er2O3 and Er3+ in Y2O3

The ultraviolet (uv) absorption spectra, representing transitions to all energy levels below 44 500 cm−1 of trivalent erbium (Er3+), have been analyzed for the crystal-field splitting of the multiplet manifolds L2S+1J of Er3+(4f11) in C2 symmetry cation sites in single-crystal cubic Er2O3 and Er3+:Y2O3. A solid solution, without a change in the local symmetry, exists between the two compounds, allowing us to identify the weaker transitions in Er3+:Y2O3 from the stronger transitions observed in the uv spectrum of Er2O3. As a result, we have identified a complete set of energy (Stark) levels for the electronic configuration up to the absorption band-edge of these crystals. A total of 134 Stark levels representing 30 multiplets with energies as high as 44 500 cm−1 have been modeled using a parameterized Hamiltonian defined to operate within the Er3+(4f11) electronic configuration. The crystal-field parameters were determined through use of a Monte Carlo method in which 14 independent crystal-field parameters...

Specific features of Eu3+ and Tb3+ magnetooptics in gadolinium-gallium garnet (Gd3Ga5O12)

Abstract We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of Eu3+ in EuGG was also measured between 85 K and RT. The magnetooptical and magnetic susceptibility data were modeled using the wavefunctions of the crystal-field split energy (Stark) levels of Eu3+ and Tb3+ occupying D2 sites in the same garnets. The results reported gave a precise determination of these Stark level assignments and confirmed the symmetry labels (irreducible representations) of the closely-spaced Stark levels (quasi-doublets) found in the 5D1 (Eu3+) and 5D4 (Tb3+) multiplets. Ultraviolet (UV) excitation (

Spectroscopic analysis of Eu3+ in single-crystal hexagonal phase AlN

A detailed spectroscopic analysis of the crystal-field splitting of the energy levels of Eu3+(4f6) in single crystals of hexagonal phase aluminum nitride is reported based on assignments made to the high-resolution cathodoluminescence spectra observed between 500 nm and 750 nm obtained at 11 K and room temperature. Single crystals doped with trivalent europium were grown by high pressure, high temperature technology, and the crystal structure was confirmed by x ray diffraction methods to be the hexagonal phase. The Eu3+ ions substitute for Al3+ ions in sites of C3v symmetry during crystal growth. More than 97% of the observed spectra are attributed to Eu3+ in the majority site. The spectra are identified as transitions from the excited 5D0 and 5D1multiplets of Eu3+ to the ground-state multiplets 7F0, 7F1, 7F2, 7F3,7F4, 7F5, and 7F6 split by the crystal field into energy (Stark) levels. A parameterized Hamiltonian defined to operate within the 4f6 electronic configuration of Eu3+ was used to model the expe...

Modeling optical spectra and Van Vleck paramagnetism in Er3+:YAlO3

Low-temperature absorption spectra are reported for Er3+:YAlO3 (YAP) between 1700 and 350 nm. The low-temperature vacuum ultraviolet absorption spectra are also reported between 400 and 190 nm. A total of 134 experimental energy (Stark) levels representing 30 multiplets with energies below 44 000 cm−1 were modeled using a parametrized Hamiltonian defined to operate within the 4f11 electronic configuration of the Er3+ ions substituting for Y3+ in YAP, an orthorhombically distorted perovskite. The Y3+ sites have low symmetry (CS). The crystal-field energy-level parameters were determined through use of a Monte Carlo method in which 14 independent parameters are given random starting values, which are optimized using standard least-squares fitting between calculated and experimental levels. The best solution obtained has a standard deviation of 6.92 cm−1 (rms error of 6.09 cm−1). In the presence of a magnetic field the Er3+ ions occupy two magnetically inequivalent sites. As an independent check of the cryst...