Spectral intensities of lanthanide complexes

The effects of solvents and complex formation with nitrogen donor ligands on the spectral intensities of the f→f transitions in Nd(III) ion have been reported. The intensity parameters T_λ have been calculated for 14 systems and are compared with oxygen donor ligands.     

Spectral intensities in the fundamental bands of HF and HCl

The transition intensities of the fundamental bands of natural isotopic HF and HCl vapors have been measured with Doppler-limited resolution using a tunable difference-frequency laser spectrometer. Precise values for the band intensities, vibrational moments and Herman-Wallis F factors have been obtained for H¹⁹F, H³⁵Cl and H³⁷Cl.     

Spectroscopy and energy level location of the trivalent lanthanides in LiYP4O12

The excitation and emission properties of the lanthanides Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Tb³⁺, Er³⁺, Tm³⁺, and Yb³⁺ in LiYP₄O₁₂ were studied by vacuum ultra-violet spectroscopy at 10 K. It provides information on the energies of 4f-5d excitation and emission bands. In the case of Er³⁺ spin forbidden emission was observed. Charge transfer excitation bands were identified for Eu³⁺, Sm³⁺, Tm³⁺, and Yb³⁺, and in the case of Yb³⁺ charge transfer luminescence is observed. All data appear to be consistent with each other and have been used to construct a level scheme showing the location of the energy levels of all trivalent and divalent lanthanides in LiYP₄O₁₂.     

Spectral line intensities of Yb3+ ion in LiNbO3 crystals

Optical spectra of absorption and luminescence of LiNbO₃:Yb³⁺ crystals are investigated experimentally and theoretically. Within the framework of the point charge approximation of crystal field, the Stark problem is solved: crystal field parameters and wave functions of Stark states are determined. Line strengths due to indirect electric-dipole and magnetic-dipole inter-Stark transitions are calculated and values of the Judd-Ofelt parameters are determined. Values of the branching ratios of luminescence. Einstein coefficients and, lifetime of the excited sublevel are calculated. A satisfactory agreement of calculated results with experimental data is obtained.     

Spectral hole burning effects initiated by uniform signal intensities in a gain-flattened EDFA

Spectral hole burning (SHB) effects in a gain-flattened erbium-doped fiber amplifier (EDFA) are demonstrated to be significant in the presence of large signal power around the 1530-1532-nm wavelength range. These are the first effects reported in a setup employing equivalent power level distribution of 40 channels ranging from 1530 to 1561 nm. To explain this, the introduction of a new local population variable into the laser equation is required to support the original inversion ratio that is determined by the pump lasers. In the analysis section, spectroscopic parameters and high signal powers are considered to be other contributing parameters to the change in the gain characteristics. An improvement to this theoretical basis is suggested by implementing mathematical modeling to validate similarities between the gain shape of simulation to that obtained in the experiment.     

Spectral and kinetic characteristics of trivalent praseodymium in LaF3-LiF and SrAl12O19

Recent data on cascade transitions in the 4f shell of the Pr³⁺ ion in various matrices are analyzed. Spectral and kinetic characteristics of LaF₃-LiF:Pr and SrAl₁₂O₁₉:Pr phosphors, which show photon cascade emission, were investigated. The emission intensities in the first (¹ S→¹ I ₆ transitions) and the second (transitions from the ³ P ₀ level to the ³ H and ³ F multiplets) cascade stages were measured and the temperature dependences of the intensities of the main emission lines and their kinetic characteristics were determined. The following parameters of SrAl₁₂O₁₉:Pr were found: the band gap width (7.5 eV), the energy gap between the ¹ S ₀, 4f and 5d levels (0.24 eV), and the characteristics of the 4f→5d band (6.0–7.5 eV) of the Pr³⁺ luminescence excitation. It is shown that the LaF₃-LiF:Pr compound has a number of specific features in comparison with other Pr³⁺-doped phosphors.     

Spectral and luminescent characteristics of trivalent lanthanide ions in a POCl3-SnCl4 inorganic solvent

We have measured the absorption and luminescence spectra of trivalent lanthanide ions (Pr³⁺, Sm³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, and Yb³⁺) in the visible and near-IR wavelength ranges in a POCl₃-SnCl₄ inorganic solvent. In terms of the Judd-Ofelt model, the oscillator strengths of absorption bands, the probabilities of radiative transitions, the luminescence branching coefficients, the lifetimes of excited states, and the luminescence quantum yields have been calculated. Possibilities of creating new laser media have been evaluated. A conclusion is drawn regarding the symmetry of the environment of trivalent lanthanide ions in the POCl₃-SnCl₄ solvent.     

Luminescent methods in the chemistry of lanthanides

The work was reported at the International Conference on Luminescence in Moscow in November 1994.     

X-ray magneto-optics in lanthanides

Magneto-optical methods in the visible light regime generally lack element specificity, which has become a considerable shortcoming in research on advanced heteromagnetic systems. Using circularly polarized soft x rays tuned to a 4d-4f core-level transition of a lanthanide element, the specularly reflected x-ray intensity changes proportionally to the magnetization of this element and, e.g., hystereses are easily measured element specifically. In contrast to the case of visible light, temperature dependent 4d-4f magneto-optical signals are not influenced by the thermal lattice expansion.     

XPS analyses of lanthanides phosphates

XPS measurements were performed on lanthanide orthophosphates LnPO₄ (Ln: La, Ce, Nd, Gd), and correlated with XRD and some EDS analyses. Single lanthanide phosphates LnPO₄ and mixed lanthanide phosphates LnxLn^′1−xPO₄, all crystallized in a monoclinic structure similar to the monazite mineral. Results were examined qualitatively and quantitatively, by considering the Ln 3d lines, P 2p line and O 1s line.Ionic sputtering does not induce significant broadening nor an additional shift of the lanthanide peaks and does not have an effect on their chemical environments, except in the case of cerium. However, sputtering seems to significantly reduce the intensity of the O 1s and P 2p peaks, while Auger peaks of carbon and oxygen atoms interfere, respectively, with the 3d line of gadolinium and neodymium. Those phenomena are all the more important when the Nd and Gd content is weak and must be taken into account for a quantitative analysis of the spectra.The quantitative analyses reveal the expected results for single monazites. On mixed phosphates, the measured phosphorous and oxygen amounts are generally more valid for non-sputtered sample surfaces than for sputtered surfaces, while the calculated relative amount of lanthanides [Ln]/[Ln′] are correct in all the cases.One of the important goals of this work was to have a satisfactory value for the atomic ratio La/Gd, and particularly in the case of (La,Ce)PO₄ and (La,Gd)PO₄, to obtain good agreement between the calculated lanthanides ratio Nd/Gd and ratios estimated from XRD and EDS measurements.     

Spectral intensities in the ν1 band of NH3

Intensities have been measured for individual transitions in the Q and R branches of the ν₁ band of NH₃ using a difference-frequency laser spectrometer. The data yield an integrated band strength of S⁰_v=219.36±1.03 cm^-2/MPa at 297 K, corresponding to a transition moment of μ_v = 8.535(20) × 10^-32 C·m, and a Herman-Wallis correction factor, (1 + _jm)², where _j = 0.0209(20). The intensities of a few lines for K 7 were noticeably perturbed by a perpendicular Coriolis interaction with 2ν₄ (E, L = 2), so were excluded from the fit. A small sample of ν₃ band lines occurring in the ν₁ band scans also yields a rough estimate of the ν₃ band intensity with evident irregular perturbations.     

Spectral intensities in the ν1 band of carbonyl sulfide and its isotopic species

A tunable diode laser was used to perform measurements of absolute lines intensities in the ν₁ fundamental of carbonyl sulfide. Spectra have also been recorded for the following isotopic species: ¹⁶O¹²C³⁴S, ¹⁶O¹³C³²S and ¹⁶O¹²C³³S. The vibrational band strength S_v⁰ was calculated at 298 K. The absolute intensity for 100% of ¹⁶O¹²C³²S species is found to be S_v⁰ = 29.69 ± 0.15 cm⁻² atm⁻¹ with the uncertainty covering three times the standard deviation. We have tried to determine the α-coefficient involved in the Hermann-Wallis factor F = (1 + αm + )² and the value is found to be negligible (−5 ± 8) × 10⁻⁵. The S_v⁰ value obtained for the other isotopic species is very close to the normal one.     

Spectral intensities and lifetimes of excited states of Er3+:SeOCI2 + SbCl5 laser liquid

Spectral oscillator strengths of excited states and lower lying levels for Er³⁺ ion in SeOCl₂, acidified with antimony pentachloride (laser liquid), are reported. Life-times of the fluorescent levels ${}^4\text{I}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext><mtext>,\; </mtext><mtext>11</mtext><mtext>2</mtext><mtext>,\; </mtext><mtext>9</mtext><mtext>2</mtext>}}$, ${}^4\text{F}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext><mtext>,\; </mtext><mtext>7</mtext><mtext>2</mtext><mtext>,\; </mtext><mtext>5</mtext><mtext>2</mtext>}}$, ${}^4\text{S}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, ${}^2\text{H}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ and ${}^4\text{G}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ have been estimated from absorption measurements.     

First approximation to the Hugoniot equation of state of the lanthanides

Summary The semi-empirical Hugoniot equation of state is obtained by using the third-order tangency between the isentropic and the Hugoniot curves at the origin of coordinates. The results of this model are in good agreement with Carter’s experimental data for fourteen elements from the lanthanides series in the lower phase only. Due to postal troubles with Lebanon, it was impossible to send proffs to the author as he requested.     

Nuclear magnetism and the trivalent europium ion

Enhanced nuclear moments occur in atoms, molecules and all the transition groups of the periodic table. They are unusually large for lanthanide ions, with electrons of the 4f group, but the mechanism responsible for enhancement for other ions produces “anti-shielding” effects for the trivalent europium ion. These greatly reduce the effective nuclear magnetic moments in the ground state J=0. Here it is suggested that dynamic nuclear polarization can be used to increase the effective nuclear moments, and off-set the anti-shielding. The substance is europium vanadate, “doped” with a small percentage of samarium ions.     

Van Vleck paramagnetism of the trivalent Eu ions

Magnetic susceptibilities of Eu₂O₃, EuF₃ and EuBO₃ have been measured over the wide temperature range 5-650 K. The Van Vleck paramagnetism, with the ground state of ⁷F₀ (S=3, L=3), has been investigated comprehensively. The temperature independent paramagnetism emerges manifestly below approximately 100 K. The variation of the susceptibility with temperature for EuBO₃ is in satisfactory agreement with the coupling constant , where the spin-orbit interaction is λL·S for the Russell-Saunders coupling on the basis of Van Vleck theory with one parameter λ. The value of can fit the susceptibility data of EuF₃. The deviation from the theory arises in Eu₂O₃. This discrepancy originates mainly from the influence of the crystalline field. Susceptibility of Gd₂O₃, having the ground state of ⁸S_7/2 (S=7/2, L=0), is also presented as a magnetic standard compound in comparison with these results.     

EPR of manganese-containing plasticine: Spectral simulation and use as an internal standard for comparison of the signal intensities of various free-radical EPR spectra

Electron paramagnetic resonance spectra of manganese-containing plasticine putty have been obtained both at 9.4 and 94.2 GHz (room temperature). It has been possible to analyze both, quantitatively by computer-based simulation and exact diagonalization of a general spin-Hamiltonian, by use of an appropriate powder technique. A fine fit was obtained for both frequencies with an isotropicg-2.00117, uniaxial⁵⁵Mn hyperfine valuesA _∥/g _c β _c = −93.5 G (where ‖ implies direction (ℤ) andA _⊥/g _c β _c = −94.3 G, a nuclear quadrupole effectP _z(⁵⁵Mn)=0, and a uniaxial electronic quadrupole matrix (D/g _c β _c = 3D _Z/2g _c β _c = −82.8 G). The electronic octupole energy was taken into account via the single parameterB ₄⁰/g _c β _c = −0.024 G. The plasticine has been demonstrated to afford a fine intensity and magnetic-field standard, say, for use with free radicals such as spin-trap adducts. Examples provided are 2,2-diphenyl-l-picrylhydrazyl, and hydroxyl radical generated by the Fenton reaction and spin-trapped with 5,5-dimethyl-1-pyroline-N-oxide.