Electronic Spectra of Cs 2 NaYbF 6 and Crystal Field Analyses of YbX 6 3- (X = F, Cl, Br) (original) (raw)
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Physical Review B, 2000
Electron paramagnetic resonance ͑EPR͒, optical absorption, fluorescence, and excitation spectra of CsCdBr 3 :1% Yb 3ϩ single crystals were taken at 4.2 K. An analysis of the dependence of the EPR spectrum on the magnetic-field direction and a comparison of the recorded signal shapes with simulated envelopes over the magnetic dipole transitions of the expected dimers containing all ytterbium isotopes were performed. This allowed us to assign the measured EPR spectra unambiguously to the symmetrical pair center of the type Yb 3ϩ -Cd 2ϩ vacancy-Yb 3ϩ substituting for three adjacent Cd 2ϩ ions in the bromine octahedra chains. A distance of 0.596 nm between the magnetically equivalent Yb 3ϩ ions was determined from the line splitting due to magnetic dipole-dipole interaction. An interpretation of the optical spectra in compounds containing ͑YbBr 6 ͒ 3Ϫ complexes is presented, which is based on a crystal-field theory accounting for an interaction between the ground 4 f 13 (Yb 3ϩ )͓4p 6 (Br Ϫ )͔ 6 and excited 4 f 14 (Yb 2ϩ )4p 5 (Br)͓4p 6 (Br Ϫ )͔ 5 charge-transfer configurations. The observed large splitting of the excited 2 F 5/2 (4 f 13 ) crystal-field multiplet is explained on the basis of a quasiresonant hybridization of the 4 f -hole state with the spin orbitals of the charge-transfer states. With physically reasonable values of the fitted model parameters, the calculated energy level diagram of the 4 f 13 configuration and the g tensor of the Yb 3ϩ ion in the crystal-field ground state are in good agreement with the experimental data.
Vibronic intensities in the absorption spectra of Yb3+
Physical Review B, 1996
The oscillator strengths and relative vibronic intensity distribution of the ( 2 F 5/2 )⌫ 8 ,⌫ 7 ←⌫ 6 ( 2 F 7/2 ) transitions of the YbCl 6 3Ϫ complex ion at an octahedral symmetry site in the Cs 2 NaYbCl 6 lattice have been measured experimentally and calculated using a combined vibronic crystal-field-ligand polarization approach. The vibronic crystal-field contribution to the total transition dipole moment of the various excitations was worked out both with and without invoking closure over the central metal ion intermediate electronic states and the intensity was assumed to be derived from both a parity and a spin-allowed d← f transition with the cooperation of the odd-parity vibrational modes of the complex ion. Quadrupole and hexadecapole terms have been included in the ligand polarization contribution. Attention has been given to the correct choice of phases for both the electronic and the vibrational wave functions in order to ensure the right sign for the cross term which couples together the crystal field and the ligand polarization transition dipole vectors. The ab initio formalism employed avoids the use of any adjustable parameters in calculating the vibronic intensities. The calculated oscillator strengths of vibronic transitions are within order of magnitude agreement with experimental values. The sensitivity of the calculated values to the use of different force fields has been investigated. The experimentally measured total oscillator strengths for the ( 2 F 5/2 )⌫ 8 ,⌫ 7 ←⌫ 6 ( 2 F 7/2 ) transitions of YbCl 6 3Ϫ diluted into the transparent Cs 2 NaGdCl 6 host remain constant with change in Yb 3ϩ concentration although deviation of the chromophore from octahedral symmetry is evident at intermediate concentrations. A comparison with the vibronic sidebands of Cs 2 LiYbCl 6 and Cs 2 KYbF 6 is made. ͓S0163-1829͑96͒05329-5͔
Energy Shift of the 4 f 13 6 s 1 Excited States of Yb 2+ from Gas Phase to the CsCaBr 3 Solid
Spectroscopy Letters, 2010
Very large embedding effects on the 4f 13 6s 1 excited states of Yb 2+ are found in Yb 2+ -doped CsCaBr 3 , which are originated beyond the first bromide coordination shell and increase the 4f 14 →4f 13 6s 1 electronic transitions by some 20000 cm −1 with respect to their gas phase values. As a consequence, these states, which are found among the lowest lying states of Yb 2+ in gas phase, are pushed up in energy to the conduction band of the host. Ab initio quantum chemical calculations have been done in the free ion, in the (YbBr 6 ) 4− cluster in vacuo, and in the (YbBr 6 ) 4− cluster embedded in CsCaBr 3 in order to understand the strong destabilization and to show, separately, the bromine ligands effects and the effects of the host ions located beyond them, on the wave functions and energies of the 4f 13 6s 1 states. The results of the (YbBr 6 ) 4− cluster in vacuo reveal that the 4f 13 6s 1 states undergo a sudden energy and electron density change at short Br-Yb distances, which results in the formation of an Yb-trapped exciton which evolves to full ionization of the (YbBr 6 ) 4− cluster as the molecular basis set used is enlarged to allow for delocalization. These results indicates that Yb(II) is unstable in hexabromide coordination in gas phase. Subsequent embedded cluster calculations reveal that the charge spill is reversed by the embedding interactions with the host ions located beyond the YbBr 6 moiety and localization of the 6s electronic density inside the Br 6 cage is restored. The localization enforced by the embedding interactions increases the electron repulsion within the Br 6 cage and the energy of the 4f 13 6s 1 states is strongly risen.
Chinese Physics B, 2012
The local coordination structures around the doping Yb 2+ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb 2+ were calculated to study the effect of the doping on the local coordination structures of Yb 2+ . Using the calculated local structures, we obtained the crystal-field parameters for the Yb 2+ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method. The calculated crystal-field parameters were analyzed and compared with the fitted results.
Optics and Spectroscopy, 2011
The evolution dynamics of absorption spectra induced in samples of Na 4 Y 6 F 22 :Ce 3+ , Yb 3+ crystal by radiation resonant with 4f-5d transitions of Ce 3+ ions was studied and analyzed. It was found that at least two types of color centers with different life times are induced in the studied crystal. It is established that the group of absorption bands in the UV spectral range that demonstrate long term stability after excitation is caused by the 4f 13-4f 12 5d transitions of bivalent ytterbium ions. The sequence of processes that lead to the reduction of ytterbium ions from the bivalent to the trivalent state is proposed.
Electronic structure of YbTX compounds
Journal of Alloys and Compounds, 2003
The electronic structure of ternary YbTX compounds (T5Au, Pd, Rh, Pt; X5Sn, Bi) was studied by X-ray photoemission spectroscopy (XPS). XPS valence bands were compared with calculations using the tight-binding linear muffin-tin orbital method. The results showed that the valence bands in these compounds were formed mainly by the 4f orbitals of ytterbium and the 4d (5d) orbitals of the transition elements. Analysis of the Yb 4f valence band and Yb 4d core level states clearly indicated the presence of divalent Yb ions in YbAuSn and YbAuBi, and trivalent ions in YbRhSn and YbPtSn. In turn, the Yb ions in YbPdBi exhibited a mixed valence character.
Concentration distribution of Yb2+ and Yb3+ ions in YbF3:CaF2 crystals
Journal of Crystal Growth, 2008
Calcium fluoride crystals doped with YbF 3 were grown using the Bridgman technique. The optical absorption spectra reveal the characteristic UV-absorption bands of divalent Ytterbium. The absorption coefficient of divalent Yb is more than ten times higher than that of trivalent Ytterbium. This shows that the developed crystal growth process achieves a good Yb 3+ -Yb 2+ conversion. The concentration distribution of the Yb 2+ and Yb 3+ ions among two of the samples was investigated using the optical absorption method. Taking into account the relationship between the optical absorption coefficient and the concentration of the impurities in the sample, the segregation coefficient of the two types of ytterbium ions has been calculated. From our calculations, we obtained the results that the segregation coefficient of the Yb 3+ ions in a CaF 2 host is E1, and for Yb 2+ ions is ol. r
Optical spectroscopy of Yb2+ ions in YbF3-doped CaF2 crystals
Journal of Crystal Growth, 2008
Transparent colorless Ca 1Àx Yb x F 2+x (x ¼ 0.0007-0.016) crystals were grown using the vertical Bridgman technique. In order to obtain efficient Yb 3+ -Yb 2+ conversion in the as-grown crystals, a special procedure has been developed. Room temperature optical absorption spectra reveal the characteristic UV absorption bands of the Yb 2+ ions in the as-grown crystals, with intensities more than 10 times higher than those reported by other authors using various conversion procedures. The influence of YbF 3 content and of codoping with Pb 2+ ions on the absorption and emission spectra has been studied. Room temperature emission bands in the near UV (not reported before) and in the visible spectral domain have been observed. The emission intensity depends on the dopant concentration. A comparison of our results with those obtained by other authors is also given. r
Cooperative luminescence of Yb3+ ion pairs in Li6Y(BO3)3:Yb single crystals
Journal of Luminescence, 2021
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