Emission spectra of lanthanide ions in hexafluoroelpasolite lattices excited by synchrotron radiation (original) (raw)
Related papers
The Journal of Physical Chemistry C, 2009
Vacuum ultraviolet (VUV) excitation spectra at 10 K have been recorded for the lanthanide ions, Ln 3+ ) Nd 3+ , Ho 3+ , Tm 3+ , and Yb 3+ , situated at octahedral site symmetry in hexafluoroelpasolite Cs 2 NaLnF 6 lattices. The corresponding VUV/UV/visible/near-infrared emission spectra have also been recorded. The 4f N-1 5d energy levels and 4f N -4f N-1 5d spectral intensities have been calculated by judicious selection of parameters, without detailed fittings, when employing the M. F. Reid suite of programs. The simulations are in reasonable agreement with experimental data. Some additional spectral features for these systems have been assigned to charge transfer (CT) transitions, and CT emission is reported for the case of Tm 3+ . A comparison of the results with the spectra of LiYF 4 :Ln 3+ has been included and the major difference lies in the greater crystalfield strengths for Ln 3+ in the hexafluoroelpasolite lattices.
Vacuum ultraviolet excitation spectra of lanthanide-doped hexafluoroelpasolites
Journal of Physics: Condensed Matter, 2009
Emission spectra at 10 K employing synchrotron radiation have been recorded for the tripositive lanthanide ions, Ln = Sm, Gd, Tb, Ho, and Er situated at octahedral (or nearly octahedral) site symmetry in hexafluoroelpasolite Cs 2 NaMF 6 (M = Y, Sc, or Ga) lattices. Interconfigurational 5d ? 4f transitions are only observed for Er 3+ , and the intensity ratio of 4f 10 5d ? 4f 11 emission, compared with 4f 11 ? 4f 11 emission, with excitation into 5d levels, is greater for M = Ga than M = Sc. The highest energy intraconfigurational emission is from 4 G 5/2 (Sm 3+ ), 6 P 7/2 (Gd 3+ ), 5 D 3 (Tb 3+ ), 5 G 4 (Ho 3+ ), and 2 F(2) 7/2 (Er 3+ ). Detailed energy level assignments have been given for Ln = Sm, Gd, and the remaining spectra are assigned as multiplet-multiplet transitions.
Journal of Physics: Condensed Matter, 2009
Emission and excitation spectra of Cs 2 NaLnCl 6 (Ln = Y, Eu, Gd, Er, Yb), Cs 2 NaYCl 6 :Ce and Cs 2 NaYCl 6 :Tm have been recorded using synchrotron radiation. With the possible exception of the case for Ce 3+ , no 5d → 4f transitions are observed and the emission spectra are entirely assigned to 4f → 4f intraconfigurational transitions of Ln 3+ in LnCl 3− 6 and impurity species. The excitation spectra comprise intraconfigurational, charge transfer and band-to-band transitions. Trace impurities of oxy-species or of other lanthanide ions have a profound effect upon the spectra. The 4f-5d absorption spectra have been simulated by employing the suite of programs of Professor M F Reid and the results have been included together with the experimental spectra.
Inter- and Intraconfigurational Transitions of Nd 3+ in Hexafluoroelpasolite Lattices
The Journal of Physical Chemistry B, 2006
Excitation of the 4f 3 ion Nd 3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength ∼185 nm leads to fast 4f 2 5d f 4f 3 emission below 52 630 cm -1 and slower 4f 3 f 4f 3 emission from the luminescent states 4 F 3/2 Γ 8u (11 524 cm -1 ) and 2 G(2) 9/2 Γ 8u (∼47 500 cm -1 ). The near-infrared emission is well-resolved, and a clear interpretation of the 4 I 9/2 crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2 G(2) 9/2 emission enables clarification of the structure of the 4f 2 5d configuration (which extends from ∼52 000 to 128 000 cm -1 ). Detailed energy level and intensity calculations have been performed, which provide simulations of the d-f emission and the f-d excitation spectra in good agreement with experiment. It is interesting that although the 4f 3 2 G(2) 9/2 Γ 8u f 4f 3 4 I J transitions are very weak in intensity compared with transitions terminating upon higher multiplet terms, most of the 4f 2 5d ( 3 H) 4 I 9/2 Γ 8g f 4f 3 emission intensity resides in the transitions to 4 I J .
4f(n)-> 4f(n)-15d transitions of the heavy lanthanides: Experiment and theory
2002
The 4 f n →4 f nϪ1 5d(f d) excitation spectra of the heavy lanthanides (Tb 3ϩ , Dy 3ϩ , Ho 3ϩ , Er 3ϩ , Tm 3ϩ , and Yb 3ϩ) incorporated in LiYF 4 , CaF 2 , and YPO 4 are investigated in the ultraviolet and vacuum-ultraviolet spectral region ͑100-275 nm͒. Spin-forbidden transitions as well as spin-allowed transitions are observed for all heavy lanthanides. In the excitation spectra the crystal-field splitting of the 5d electron can be clearly observed. Fine structure ͑zero-phonon lines and vibronic lines͒ is observed for the transition to the lowest 5d crystal-field component, for both the high-spin and low-spin fd bands. Energy-level and intensity calculations are performed by an extension of the commonly used model for energy-level calculations of 4 f n states. A good agreement between experimental and simulated spectra is obtained, using parameters that describe the 5d crystal-field splitting ͑from the spectra of Ce 3ϩ), the parameters for the splitting of the 4 f nϪ1 core ͑from the literature on energy-level calculations for 4 f n states͒ and parameters for the spin-orbit coupling of the 5d electron and the Coulomb interaction between 4 f and 5d electrons ͑from atomic ab initio calculations using the computer code of Cowan͒. To improve the agreement between the model and experiment, the 5d crystalfield parameters were adjusted slightly to correct for the decreasing crystal-field strength for the heavier rare earths due to the lanthanide contraction. The f-d interaction parameters in the fluoride host lattices were reduced to about 67% of the calculated free-ion values in order to compensate for the nephelauxetic effect.
Spectroscopy and Calculations for 4f N → 4f N –1 5d Transitions of Lanthanide Ions in K 3 YF 6
The Journal of Physical Chemistry A, 2012
In the present work, we report on the combined experimental and theoretical studies of the 4f−5d spectra of Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , and Er 3+ ions in a newly synthesized K 3 YF 6 matrix. The low temperature experimental 4f−5d excitation spectra have been analyzed and compared with the results of the energy-level and intensity calculations. For this theoretical analysis, the extended phenomenological crystal-field model for the 4f N−1 5d configuration (i.e., the extended f-shell programs, developed by Prof. M. F. Reid) and exchange charge model (developed by Prof. B. Z. Malkin) have been used together to estimate the crystal field parameters and implement the spectral simulations. On the basis of the results of the performed theoretical analysis, we suggest the most probable positions occupied by optically active ions. Although the spectra of only eight lanthanide ions have been studied, the Hamiltonian parameters of the 4f N−1 5d configuration have been evaluated for the whole lanthanide series and reported here for the first time, to give a complete and unified description of the spectroscopic properties of the trivalent rare earth ions in the chosen host. In addition to the studies of the 4f−5d transitions, various possible competitive excitation channels overlapping with 4f−5d ones have also been discussed, where a theoretical scheme giving rudiments to understand 4f−6s spectra are proposed for the first time. An excellent agreement between the calculated and measured excitation spectra shapes confirms validity of the performed analysis. The obtained parameters of the crystal field Hamiltonians for different ions and various electron configurations can be used in a straightforward way to generate the energy level positions and calculate the particular transition intensities for any rare earth ion in any particular spectral region. With the aid of the obtained parameters, the positions of the lowest energy levels of the 4f N , 4f N−1 5d ,and 4f N−1 6s configurations of rare earth ions and 4f N+1 (np) 5 configuration of rare earth ions and ligands (corresponding to the ligand−impurity ion charge transfer transitions) in the band gap of K 3 YF 6 have all been estimated. The obtained Hamiltonian parameters and energy levels diagrams, which include the electronic structure of a host material, can be used as a starting point for analysis of spectroscopic properties of trivalent lanthanides in similar fluorides.
Spectroscopy of High-Energy States of Lanthanide Ions
European Journal of Inorganic Chemistry, 2010
We discuss recent progress and future prospects for the analysis of the 4f N −1 5d excited states of lanthanide ions in host materials. We demonstrate how ab-initio calculations for Ce 3+ in LiYF 4 may be used to estimate crystal-field and spin-orbit parameters for the 4f 1 and 5d 1 configurations. We show how excited-state absorption may be used to probe the electronic and geometric structure of the 4f N −1 5d excited states in more detail and we illustrate the possibilities with calculations for Yb 2+ ions in SrCl 2 .
Comparative energy level parametrizations for lanthanide ions in octahedral symmetry environments
Journal of Alloys and Compounds, 1995
New experimental datasets are presented for the energy levels of tripositive lanthanide ions situated in octahedral symmetry environments, in elpasolite lattices. The freely varying atomic parameters derived from energy level parametrizations of the new datasets show empirical relations with atomic number. The magnitudes of the crystal field parameters for a given system change considerably, according to the number of energy levels employed in the fit. This fitting uncertainty blurs the trends in the parameters across the lanthanide series. The elpasolite lattice is a model system for investigating the crystal field perturbations experienced by a lanthanide ion when the chemical identity of the nth nearest neighbour in the coordination sphere is changed.