States Of Yb Research Articles

UV/ visible/ NIR sensitized enhanced green luminescence of a newly synthesized salicylic acid coated Tb3+ and Yb3+ ions doped Y2O3 nano-composite phosphor: Prospect as luminescence solar collector material

The present work describes the enhancement of green luminescence of Tb3+ ion in a newly synthesized composite material that contains Tb3+ and Yb3+ ions in Y2O3 nano-phosphor (TYY) coated with salicylic acid (SA) doped polyvinyl alcohol (PVA) polymer matrix (TYY: SA/PVA). XRD results reflect nearly 50 nm size of crystallite in TYY phosphor. On coating, the same with SA-doped PVA polymer visualizes the actual particulate size in microns due to aggregation of nano-crystallites of TYY and indicates the formation of organic/inorganic composite material. In down-conversion of UV radiation, both singlet and triplet states of excited state intra-molecular proton transfer species of SA in TYY: SA/PVA composite material transfer their UV (200 nm–370 nm) excitation energy through Fӧrster and Dexter mechanism to 5D4 state of Tb3+ ions, which enhances green luminescence of Tb3+ ions [5D4 →7F5] by nineteen-fold and decrease in the NIR luminescence intensity of Yb3+ ion [2F5/2 → 2F7/2] in TYY/SA/PVA as compared to the TYY sample indicates coating of SA/PVA polymer on the nano phosphor blocks the quantum cutting process from 4f75 d1 excited state of Tb3+ ions to 2F5/2 state of Yb3+ ions. In contrast, TYY: SA/PVA and TYY material exhibit intense green luminescent emission of Tb3+ ions by up-conversion of NIR radiation through a cooperative energy transfer between two Yb3+ ions [2F5/2 → 5D4 excitation]. A thin layer coating of composite phosphor material shows enhancement in the external quantum efficiency of the solar cell by increasing the efficiency of ∼3–5 % in the 400 nm–1000 nm range compared to the bare solar cell. I–V characteristics of the composite show that simultaneous excitation of this composite material with UV/Visible/NIR radiation increases the photon density in blue, green, and NIR regions for reabsorption by the photovoltaic cell. This preliminary study signifies the scope for developing brighter, high photon flux luminescent composite luminescent solar collecter material with low cost.

Enhanced 3.1µm mid-infrared emission from Er3+/Yb3+ co-doped tellurite glass pumped by 980nm laser diode

Yb3+ ions co-doping was attempted for the first time for sensitizing Er3+ ions and increasing the 3.1 µm fluorescence, originating from the transition from Er3+: 4S3/2 → 4F9/2. Under a 980 nm LD excitation, strong 3.1 µm fluorescence in the mid-infrared (MIR) region and the related energy level change process were investigated. An enhanced 3.1 µm emission was attained from the Er3+/Yb3+ co-doped tellurite glass with the increment in Yb2O3 content, which demonstrated that the Yb3+ ions may act as the sensitizer to the Er3+ ions, thereby providing an effective energy transport channel from the 2F5/2 state of Yb3+ ions to the 4S3/2 state of Er3+ions. Moreover, the measured emission band full width at half maximum reaches about 164 nm along with the maximum emission cross-section (2.88 × 10−21 cm2). The outcome of our work suggests that upon co-doping with Er3+/Yb3+, the tellurite glass may function as a prospective material for fabricating the matrix of 3.1 µm MIR lasers.

Downconversion mechanism in Er3+/Yb3+ codoped fluorotellurite glasses to enhance the efficiency of c-Si PV cells

Fluorotellurite glass codoped with erbium and ytterbium was elaborated through the melting-quenching route. Through the DSC and Raman measurements, the investigated glass samples presented high thermal stability and low phonon energy, respectively. By using the laser excitation at 488 nm, the downconversion mechanism in the Er3+/Yb3+ system was investigated and the energy transfers implicated in the emissions of erbium and ytterbium ions were discussed based on the different cross-relaxation processes. The addition of ytterbium resulted in an effective energy transfer from the excited 4S3/2/2H11/2 state of Er3+ ions to the emitting 2F5/2 state of Yb3+ ion, which considerably enhanced NIR emissions at 1000 nm and reduced experimental lifetimes of 4S3/2/2H11/2 states. Through luminescence decay analysis, the maximum values of quantum efficiency (ηQE) and energy transfer efficiency (ηET) were estimated as 61.2% and 161.2%, respectively. This result indicates that the proposed glasses can convert visible photons into NIR emissions at 1000 nm suitable to improve the spectral response of crystalline silicon PV cells.

Efficient Near-Infrared Quantum Cutting in Y2O3 Codoped with Ho3+,Yb3+ Phosphor Synthesized by Solution Route

A series of Ho3+/Yb3+-codoped cubic Y2O3 nanoparticles were prepared by complex based precursor solution method. The phase purity of the samples was characterized by X-ray diffraction. Crystal structure of Y2O3:Ho3+(1 mol %), Yb3+ (30 mol %) phosphor was refined using Rietveld refinement method. The energy-transfer (ET) phenomenon between Ho3+ ions and Yb3+ ions was verified by steady-state as well as time resolved photoluminescence (PL) spectroscopy measurements. An efficient green emission has been observed upon excitation by 449 nm, which decreases monotonously with increasing Yb3+ concentration. Beyond that, the decay curves were also measured to certify the existence of the ET process. The down conversion phenomena appeared when the samples were excited by 449 nm wavelengths corresponding to the transition of Ho3+:5I8→5G6/5F1. On the basis of the analysis of the relationship between the initial transfer rate of Ho3+: 5F3 level and the Yb3+ doping concentration, it indicates that the ET from 5F3 state of Ho3+ ions to 2F5/2 state of Yb3+ ions is mainly through at wo step ET process, not the long-accepted cooperative ET process. In addition, a 97% ET efficiency and 197% quantum cutting can be achieved in Y2O3:1% Ho3+, 20% Yb3+. The current research indicates that Y2O3:Ho3+/Yb3+is a promising material to improve conversion efficiency of crystalline silicon solar cell.

Radiation-Stimulated Transformations Yb-=SUP=-3+-=/SUP=-->Yb-=SUP=-2+-=/SUP=- and Yb-=SUP=-3+-=/SUP=-->Yb-=SUP=-3+-=/SUP=- in Single Crystals and Nanoceramics CaF-=SUB=-2-=/SUB=- : YbF-=SUB=-3-=/SUB=-

The radiation resistance of CaF2 : YbF3 (3 mol.% YbF3) laser ceramics and a single crystal of similar composition (3.6 mol.% YbF3) exposed to gamma rays in a 60Co source is studied. The non-irradiated samples have been shown to be similar in spectral characteristics. After the CaF2 : YbF3 crystals and ceramics γ-irradiation and the following time exposure, along with transformations Yb3+->Yb2+, configurational Yb3+->Yb3+ transitions between different states of Yb3+ ions in the structure of samples are carried out, with the participation of interstitial Fi ions. Keywords: radiation resistance, laser ceramics, gamma rays, spectral characteristics defects.

Volume and surface effects on two-photonic and three-photonic processes in dry co-doped upconversion nanocrystals

Despite considerable advances in synthesizing high-quality core/shell upconversion (UC) nanocrystals (NC; UCNC) and UCNC photophysics, the application of near-infrared (NIR)-excitable lanthanide-doped UCNC in the life and material sciences is still hampered by the relatively low upconversion luminescence (UCL) of UCNC of small size or thin protecting shell. To obtain deeper insights into energy transfer and surface quenching processes involving Yb3+ and Er3+ ions, we examined energy loss processes in differently sized solid core NaYF4 nanocrystals doped with either Yb3+ (YbNC; 20% Yb3+) or Er3+ (ErNC; 2% Er3+) and co-doped with Yb3+ and Er3+ (YbErNC; 20% Yb3+ and 2% Er3+) without a surface protection shell and coated with a thin and a thick NaYF4 shell in comparison to single and co-doped bulk materials. Luminescence studies at 375 nm excitation demonstrate back-energy transfer (BET) from the 4G11/2 state of Er3+ to the 2F5/2 state of Yb3+, through which the red Er3+4F9/2 state is efficiently populated. Excitation power density (P)-dependent steady state and time-resolved photoluminescence measurements at different excitation and emission wavelengths enable to separate surface-related and volume-related effects for two-photonic and three-photonic processes involved in UCL and indicate a different influence of surface passivation on the green and red Er3+ emission. The intensity and lifetime of the latter respond particularly to an increase in volume of the active UCNC core. We provide a three-dimensional random walk model to describe these effects that can be used in the future to predict the UCL behavior of UCNC.

NIR luminescence lifetime nanothermometry based on phonon assisted Yb3+-Nd3+ energy transfer.

Luminescence thermometry in biomedical sciences is a highly desirable, but also highly challenging and demanding technology. Numerous artifacts have been found during steady-state spectroscopy temperature quantification, such as ratiometric spectroscopy. Oppositely, the luminescence lifetime is considered as the most reliable indicator of temperature thermometry because this luminescent feature is not susceptible to sample properties or luminescence reabsorption by the nanothermometers themselves. Unfortunately, this type of thermometer is much less studied and known. Here, the thermometric properties of Yb3+ ions in Nd0.5RE0.4Yb0.1PO4 luminescent temperature probes were evaluated, aiming to design and optimize luminescence lifetime based nanothermometers. Temperature dependence of the luminescence lifetimes is induced by thermally activated phonon assisted energy transfer from the 2F5/2 state of Yb3+ ions to the 4F3/2 state of Nd3+ ions, which in turn is responsible for the significant quenching of the Yb3+:2F5/2 lifetime. It was also found that the thermal quenching and thus the relative sensitivity of the luminescent thermometer can be intentionally altered by the RE ions used (RE = Y, Lu, La, and Gd). The highest relative sensitivity was found to be SR = 1.22% K−1 at 355 K for Nd0.5Y0.4Yb0.1PO4 and it remains above 1% K−1 up to 500 K. The high sensitivity and reliable thermometric performance of Nd0.5La0.4Yb0.1PO4 were confirmed by the high reproducibility of the temperature readout and the temperature uncertainty being as low as δT = 0.05 K at 383 K.

Crystal growth, structure, optical properties and laser performance of new tungstate Yb:Na2La4(WO4)7 crystals

Abstract The 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals with dimensions of O 21 × 24 mm3 and O 24 × 28 mm3 were grown by the Czochralski method. The crystal growth, spectroscopic properties and laser performances of the two crystals were investigated. The peak absorption cross-sections of the 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals are 1.51 × 10−20 cm2 and 1.74 × 10−20 cm2 along σ-polarization, as well as 1.61 × 10−20 cm2 and 1.34 × 10−20 cm2 along π- polarization, respectively. The emission cross sections calculated by Fuchtbauer-Ladenburg (FL) method along σ- orientation are 1.45 × 10−20 cm2 and 2.31 × 10−20 cm2 at 1012 nm for the two crystals, respectively. The reciprocity method (RM) was adopted to calculate the emission cross-sections for compassion, and the values at 1012 nm for the two crystals are 0.27 × 10−20 cm2 and 0.34 × 10−20 cm2, respectively. Strong re-absorption effect exists in the crystals, and the analysis of the re-absorption probabilities shows that the crystal with as high as 10 at% Yb3+ concentration has more serious re-absorption effect than many other Yb-doped crystals. The lifetimes of the excited state of Yb3+ in the two crystals were measured and fitted to be 0.392 ms and 0.422 ms, respectively. Based on the absorption and emission spectra, the important laser potential parameters, including the minimum inversion fraction β min , the saturation pump intensity I sat , the minimum pump intensity I min and gain emission cross-sections were evaluated and results indicates that Yb:Na2La4(WO4)7 are candidate lasing mediums. The laser experiments were also performed and continuous-wave (cw) laser actions were demonstrated with the c-cut uncoated crystal samples in a plane-concave cavity, end pumped by a 977 nm laser diode. The maximum output powers are respectively 1.15 W and 0.85 W for the 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals, along with the corresponding slope efficiencies of 17.24% and 12.35% when the transmittance of the output coupler is 5%. All the results indicate that the new tungstate Yb:Na2La4(WO4)7 crystal is a good laser medium.

Improved near-IR emission in Yb3+-condensed fluorosilicate apatite Sr4Yb6(SiO4)6F2 via Eu3+ doping

This work reports a new luminescence host, Yb3+-condensed fluorosilicate apatite Sr4Yb6(SiO4)6F2. Pure and Eu3+-doped Sr4Yb6(SiO4)6F2 dense ceramics were prepared via the solid-state reactions. The apatite-like structural features were confirmed via XRD Rietveld refinements. The optical absorption, down-conversion (DC) and up-conversion (UC) luminescence, and dynamic decays of Sr4Yb6-6xEu6x(SiO4)6F2 (x = 0, 0.01, 0.05, 0.1, 0.15) were investigated. In the DC with UV-light excitation, near-IR emission efficiency of Sr4Yb6(SiO4)6F2 can be greatly enhanced by Eu3+-doping via significant energy transfer from Eu3+ ions to Yb3+. The luminescence mechanisms were explained on the cross-relaxation (CR) processes between Eu3+ donors and Yb3+ acceptors. Up-conversion (UC) luminescence was detected via 974 nm excitation into 2F7/2 states of Yb3+, which occurs in green cooperative luminescence (CL) from Yb-pairs and UC red emissions of Eu3+ ions. Unlike the case of DC luminescence under UV light, CL of Yb3+ decreases quickly with the increase of Eu3+ doping; meanwhile, the up-converted red luminescence of Eu3+ shows only a small increase. The energy transfer mechanism was discussed via cross-relaxation between Yb3+ and Eu3+ ions.

Studies on the influence of structure units on the state of ytterbium ions in TeO2-based glasses

Abstract

A novel upconversion emission material based on Er3+ - Yb3+ - Mo6+ tridoped Hydroxyapatite/Tricalcium phosphate (HA/β-TCP)

In this paper, a novel material based on Er-Yb-Mo tri-doped HA/β-TCP phosphor for intense green up-conversion (UC) emission was successfully synthesized by solid-state reaction method. X-ray diffraction (XRD) measurements verified that the materials including a trace amount of HA phase has a hexagonal structure and main β-TCP phase has a rhombohedral structure, which is controlled by the doped ions. Under excitation wavelength of 976 nm laser diode, the HA/β-TCP:Er-Yb-Mo phosphor showed strong green UC emission band at 520/556 nm and weak red emission band at 656 nm which are attributed to (2H11/2, 4S3/2) - 4I15/2, 4F9/2 - 4I15/2 transition of the Er3+ ion, respectively. Remarkably, compared with the sample without Mo6+, the green emission intensities increased ∼650 times was achieved by using Er3+-Yb3+-Mo6+ doped phosphor. The high efficiency of the UC can be attributed to novel energy transfer process from |2F7/2, 3T2> state of Yb3+ - MoO42− dimer to the 4F7/2 of Er3+ ions. Moreover, the grain orientations due to the effect of Mo6+ ions doped in β-TCP phosphor could play an important role in the enhancement of UC emission intensity. These results indicate that the HA/β-TCP: Er-Yb-Mo phosphor has potential application in biological imaging and medicine.

Interconfigurational and intraconfigurational transitions of Yb2+ and Yb3+ ions in hydroxyapatite: A cathodoluminescence study

We present a cathodoluminescence (CL) study of the interconfigurational transitions of Yb2+ and intraconfigurational transitions of Yb3+ dopant ions in hydroxyapatite (HAp) powders. Our results demonstrate that strong electric fields present in the HAp lattice induce manifold levels in the electronic configuration of the ytterbium ions, due to splitting of the 4f135d1 orbitals. CL spectra of Yb2+ display a series of sharp peaks centered at 3.27, 2.98, 2.85, 2.53, 2.27, 2.09 and 1.63 eV, corresponding to transitions between multiple levels produced by a trigonal distortion of the regular octahedral crystal field of the Yb2+ 4f135d1 configuration. CL spectra of Yb3+ display four emissions centered at 1.17, 1.21, 1.24 and 1.27 eV, generated by intraconfigurational transitions between the 2F5/2 and 2F7/2 states of Yb3+ ions. Two types of samples were synthesized at different pH values, resulting in variations of the valence of the ytterbium ions, such that the ratios of Yb2+/Yb3+ were 0.31 and 0.55 in calcined powders synthesized at pH values of 6 and 4, respectively, as determined from X-ray photoelectron spectroscopy. Infrared CL images of the two samples show an inhomogeneous spatial distribution of the Yb3+ dopant in the powders. Thermal treatment of the samples, at 873 K in an oxygen atmosphere, result in quenching of the Yb2+ luminescence due to oxidation of the Yb2+ into Yb3+.

Investigation of the Energy-Transfer Mechanism in Ho3+- and Yb3+-Codoped Lu2O3 Phosphor with Efficient Near-Infrared Downconversion

A high-temperature solid-state method was used to synthesize the Ho3+- and Yb3+-codoped cubic Lu2O3 powders. The crystal structures of the as-prepared powders were characterized by X-ray diffraction. The energy-transfer (ET) phenomenon between Ho3+ ions and Yb3+ ions was verified by the steady-state spectra including visible and near-infrared (NIR) regions. Beyond that, the decay curves were also measured to certify the existence of the ET process. The downconversion phenomena appeared when the samples were excited by 446 nm wavelength corresponding to the transition of Ho3+: 5I8→5G6/5F1. On the basis of the analysis of the relationship between the initial transfer rate of Ho3+: 5F3 level and the Yb3+ doping concentration, it indicates that the ET from 5F3 state of Ho3+ ions to 2F5/2 state of Yb3+ ions is mainly through a two-step ET process, not the long-accepted cooperative ET process. In addition, a 62% ET efficiency can be achieved in Lu2O3: 1% Ho3+/30% Yb3+. Unlike the common situations in which the NIR photons are all emitted by the acceptors Yb3+, the sensitizers Ho3+ also make contributions to the NIR emission upon 446 nm wavelength excitation. Meanwhile, the 5I5→5I8 transition and 5F4/5S2→5I6 transition of Ho3+ as well as the 2F5/2→2F7/2 transition of Yb3+ match well with the optimal spectral response of crystalline silicon solar cells. The current research indicates that Lu2O3: Ho3+/Yb3+ is a promising material to improve conversion efficiency of crystalline silicon solar cell.

Bidirectional energy transfer induced single-band red upconversion emission of Ho3+ in KZnF3:Mn2+,Yb3+,Ho3+ nanocrystals

In contrast to common multiple upconversion (UC) emission characteristic from Ho3+, intense single-band red UC emission is realized in perovskite KZnF3: Mn2+,Yb3+,Ho3+ nanocrystals via controlling the doping concentration ratio of Mn2+ to Ho3+. Based on stokes emission, UC luminescence and energy levels of Mn2+ and Ho3+, a bidirectional energy transfer from the 5S2/5F4 state of Ho3+ to the 4T1(4G) state of Mn2+or |F27/2,T41(G4)〉 state of Yb3+-Mn2+ dimer, then to 5F5 state of Ho3+ (ET2) is provided to explain the unique UC emission behaviors of KZnF3: Mn2+,Yb3+,Ho3+. The effects of dopant concentration on the UC luminescence properties of KZnF3: Mn2+, Yb3+, Ho3+ is investigated in detail. Analysis of the dominant red UC emission of KZnF3: Mn2+, Yb3+, Ho3+ under different laser pulse width excitation indicates the energy transfer process. The special temperature dependent UC luminescence for Mn2+ doped and Mn2+ freely doped KZnF3:Yb3+, Ho3+ further confirm the bidirectional energy transfer mechanism in the UC process. The study of these single-band red UC nanocrystals provides deep insights into the understanding of bidirectional energy transfer in UC mechanism, offering the possibility for applications in biolabels and bioimaging.

A general approach for selective enhancement of green upconversion emissions in Er3+ doped oxides by Yb3+–MoO4 2− dimer sensitizing

In this paper, we report a general approach to enhance the upconversion (UC) luminescence of Er3+ doped oxides phosphors by Yb3+–MoO4 2− dimer sensitizing, which induced strong green UC emissions under the 976 nm laser diode excitation. By codoping of Yb3+ and Mo6+ in the Er3+ doped TiO2 and ZnO, the green UC emissions intensity can be selectively increased about 10 and 500 times than those of Er3+–Yb3+ codoped TiO2 and ZnO, respectively. The high excited state energy transfer between |2F7/2, 3T2> state of Yb3+–MoO4 2− dimer and 4F7/2 level of Er3+ significantly avoids the nonradiative decay processes happened at lower energy levels of Er3+, and then increases the green UC emissions efficiently. The proposed Yb3+–MoO4 2− dimer sensitizing has been realized as an efficient way to enhance the green UC emissions in other Er3+ doped oxides phosphors. It is expected that the selective enhanced green UC emissions sensitized by Yb3+–MoO4 2− dimer in Er3+ doped oxides phosphors can greatly extend their scope of applications.

Low-energy spin fluctuations in filled skutteruditesYbFe4Sb12 andLaFe4Sb12 investigatedthrough 121Sb nuclearquadrupole and 139La nuclear magnetic resonance measurements

We have elucidated low-energy spin fluctuations in the new filled skutteruditesYbFe4Sb12 andLaFe4Sb12 synthesized at highpressures, through 121Sb nuclear quadrupole resonance (NQR) and139La nuclear magnetic resonance (NMR) measurements. The longitudinal spin–lattice relaxation rate1/T1 of121Sb inYbFe4Sb12 provides evidence thatupon cooling below ∼20 K, the compound transforms from the localized 4f electron state ofYb3+ ions to a nonmagnetic heavy Fermi liquid state, originating from the mixing of 4felectrons with conduction electrons. Whereas, the Curie–Weiss type behaviour of the139La Knightshift and 121Sb- 1/T1 in LaFe4Sb12 indicate that the compound remains in the localized electron statedown to 1.4 K, it in fact originates from 3d electrons of Fe in[Fe4Sb12 ] anions. In both compounds, the transversal nuclear spin–spin relaxation rate1/T2 exhibits a clear peak at and K, respectively. The origin of the1/T2 peak is discussed in terms of the freezing of the thermal vibration of Sb cages or rare-earthions filled in each Sb cage. By comparing the experimental results of the presentstudy with those previously reported for the compounds synthesized at ambientpressure, it is pointed out that both the strongly correlated electron properties andthe thermal vibrations are greatly modified with the increase of rare-earth atomdeficiency.

Crystal field of Yb3+ tetragonal centers in the YbRh2Si2 intermetallic compound

The spectra of electron paramagnetic resonance and inelastic neutron scattering in crystals of the heavy-fermion intermetallic compound YbRh2Si2 are interpreted. The phenomenological potentials of the crystal electric field of Yb3+ tetragonal centers and the parameter of the Hamiltonian for the spin-orbit interaction of electrons are determined from the experimental energy level schemes. A comparison of the results obtained from experimental data on electron paramagnetic resonance, inelastic neutron scattering, and Mossbauer spectroscopy shows that the most probable ground state of Yb3+ ions in the YbRh2Si2 crystal is the Kramers doublet Γt6−.

Nonmagnetic–magnetic transition inYb(Cu1−xNix)2Si2 studied by muon-spin relaxation

The muon-spin relaxation technique has been used to investigatethe transition from a nonmagnetic to a magnetic ground state inYb(Cu1−xNix)2Si2.The effect of the chemical substitution of Cu by Ni on the magnetic properties isevidenced by an unusual occurrence of magnetic ordering, characterized by anx-dependentmagnetic volume fraction. Both the magnetic transition temperature and the magneticvolume fraction are observed to increase with Ni concentration. It is found that thesize of the magnetic volume fraction depends on the probability of an Yb ionpossessing at least two Ni ions as nearest neighbours. The transition temperature ofYbNi2Si2 is shown to be reduced compared to that of the pressurizedYbCu2Si2 at equivalent volume and is related to electron doping effects. Using a scaling law for thetemperature dependence of the relaxation rates of the Yb-moments, the Kondotemperature is deduced and found to decrease, as expected, with increasing Niconcentration.

Fluorescence and Energy Transfer between Nd3+ and Yb3+ in LaF3

Energy transfer has been observed in single crystals of LaF3 codoped with Nd3+ and Yb3+ resulting from the near resonance transitions between states of Nd3+ and the 2F7/2→2F5/2 states of Yb3+. From an analysis of the fluorescence and absorption spectra of Yb3+, all the crystalline field Stark components of the 2F7/2 and 2F5/2 state were determined. The four crystal sublevels of the 2F7/2 ground states are found at 0, 185, 401, and 870 cm−1. The three levels of the excited 2F5/2 states are determined at 10 260, 10 430, and 10 660 cm−1, respectively. Based on these values of the Stark levels, the spin—orbit coupling radial integral for Yb3+ in LaF3 is calculated to be 2882 cm−1.