Stark Levels Research Articles

High-resolution laser induced excitation spectroscopy and decay dynamics of YNbO4:Er3+

The rare earth materials have attracted intensive attention due to their strong luminescent characteristic. However, the split fine Stark levels are difficult to be determined. Here we report a room-temperature detection for Stark levels of YNbO4: Er3+ using established laser-induced spectroscopy system with dye laser of superhigh resolution of wavelength at 0.005 nm. From excitation spectra, six split Stark levels of 4G11/2 (Er3+) were directly detected. Moreover, nonradiative relaxations of 4G9/2→4G11/2 and 4G11/2→2H11/2/ 4S3/2 have been observed with weighed lifetimes of 0.70 μs and 6.15 μs, and characteristic green emission of Er3+ (@555 nm) yields lifetime of 31.78 μs.

Theoretical study by analytical equations of optical properties of the phosphors Zn2SnO4 codoped with Cr3+ and (Al3+ or Eu3+) via the crystal field control

The phenomenon of persistent luminescence in the phosphors Zn2SnO4 doped by Cr3+ and codoped by Al3+ or Eu3+ is related to the energy levels of the doping transition ions Cr3+ and rare earth ions Eu3+, the concentration of Al3+ substituting Zn and Sn, the intrinsic defects and the energy bands of the Zn2SnO4 matrix. To fully understand the procedure of persistent luminescence in these phosphors, we firstly determine the role of the Cr3+ ions in this process. For this reason, a crystal-field theory, using the Racah tensor algebra method, of the optical region associated to the transitions between the Stark levels of Cr3+ in these phosphors was performed. We examine then the influence by codoping with Al3+ and Eu3+ on the persistent luminescence process. In the second step, we analyze the role of the traps after discussing some of these properties. Finally, we propose an energy transfer mechanism from PLE, PL spectra and TL curves.

Synthesis of YSAG:Er ceramics and the study of the scandium impact in the dodecahedral and octahedral garnet sites on the Er3+ energy structure

Optical ceramic’ samples based on yttrium-erbium-scandium-aluminum garnet with transmission coefficients over 80% in the wavelength range from 1050 to 2500 nm were manufactured. The effects of bands' broadening and shifting in the luminescence and transmittance spectra depending on the scandium concentration in the dodecahedral and octahedral sites were detected. Based on the luminescence and absorption spectra analysis, the consistent patterns of the 23 Stark levels energy changes belonging to the 4S3/2, 4I11/2, 4I13/2, and 4I15/2 multiplets’ of Er3+(4f11) cations were determined. Furthermore, it has been demonstrated that introducing Sc3+ into the dodecahedral sites leads to more significant deformations of the YSAG:Er crystal field than in the octahedral one.

NIR Laser‐Treatment, Anti‐Oxidation Upconversion Nanoparticles for Optical Temperature Sensing

AbstractRare earth ions doped upconversion nanoparticles have a good potential in optical temperature sensing. Herein, a series of ZnO : Yb/Tm/Ga are prepared, which realize the last sensitization. ZnO semiconductor host is sensitized under 980 nm excitation at power 0.6 W. The upconversion luminescence (UCL) intensity of sample increase about ∼15 times compared with pre‐sensitization. The colors of UCL change from blue to yellow with the excitation powers from 0.20 W to 1.05 W, realizing the multi‐color turning. Temperature‐sensing properties based on Stark levels and non‐thermally coupled energy levels (NTECLs) of Tm3+ are analyzed. The maximum relative sensitivity (Sr) of temperature sensor reaches 44.37 %K−1 at 693 K, which originated from 1G4 (652 nm) and 3F2,3 (700 nm) of Tm3+. The energy gap between the energy level 1G4 and 3F2,3 of Tm3+ is about ∼1217 cm−1, which suggest that they are thermally coupled. Moreover, ZnO : Yb/Tm/Ga@SiO2 have no damage to the liver, indicating that UCNPs has a low biological toxicity. The ZnO : Yb/Tm/Ga@SiO2 core/shell upconversion nanoparticles can be used in temperature sensors and biological temperature sensing.

Absorption and emission cross-sections, Stark energy levels, and temperature dependent gain of Yb:QX phosphate glass.

We have obtained the absolute absorption cross-sections of Yb-doped phosphate QX laser glass at 300 K from 800-1100 nm, and generated the emission cross-sections via the standard method of reciprocity. By generating nine detailed high-confidence fitting functions for the absorption cross-sections, we then applied reciprocity to the individual absorption functions and obtain, for the first time to our knowledge, nine corresponding detailed emission functions that when summed, display a more accurate representation of the emission cross-sections as a function of wavelength than the standard method. A deeper mathematical understanding of reciprocity is also presented, along with derived Yb:QX Stark levels.

Temperature dependence of red emission in YPO4:Pr3+ nanopowders

In order to compare spectroscopic properties between nanosized and that in single crystal form of YPO4:Pr3+, temperature-dependence of the red emission from 3P0 → 3H4 and 1D2 → 3H4 transitions of YPO4:0.1 at. % Pr3+ nanopowders has been investigated in details. The emission spectra of the sample in size of 20 nm, under selective excitation at 3P2, measured at different temperatures, T = 10, 100, 200 and 300 K have been recorded. The variation of emission intensity of each 3P0 → 3H4 and 1D2 → 3H4 against temperature has been investigated. Several spectral lines constitute 1D2 → 3H4 emission, assigned to transitions between 1D2 and 3H4 Stark levels are observed with no noticeable shifts between them and those observed at the single crystal. It is found that 1D2 → 3H4 emission intensity dominates that of 3P0 → 3H4 transition, pointing out the high efficiency of the multiphonon relaxation (MPR) process from 3P0 to 1D2. Fitting the temperature dependence of 3P0 → 3H4 emission intensity permits to estimate the phonons and their energies involved in non-radiatively transition between 3P0 and 1D2 levels, which are found different from single crystal. Also, fitting the multiphonon relaxation (MPR) rates against temperature, extracted from the measured 1D2 lifetime gives information that seven phonons can be involved to bridge the gap between 1D2 and 1G4. Furthermore, the possibility to use the YPO4: 0.1 at. % Pr3+ in the nano-thermometry application in temperature range T = 10–300 K was investigated.

Trimodal Ratiometric Luminescent Thermometer Covering Three Near-Infrared Transparency Windows.

Near-infrared (NIR) transparency windows have evoked considerable interest in biomedical thermal imaging owing to the superior tissue penetration and the high signal-to-noise ratio, allowing in vivo real-time temperature reading with nanometric spatial resolution. Here, we develop a multimode nonintrusive luminescent thermometer based on the Y3Al5O12 (YAG):Cr3+/Ln3+ (Ln = Ho, Er, Yb) phosphor, which covers three NIR biological transparency windows, enabling cross-checking readings with high sensitivity and a high penetration depth. Utilizing the energy transfer between lanthanide ions and transition-metal ions, the Cr3+/Ln3+-activated upconversion emissions provide ideal signals for ratiometric luminescent thermometry of the NIR-I mode. The phonon-assisted downshifting emissions of Er3+/Ho3+ are used to construct the NIR-III/II mode, and the NIR-III mode is based on the thermal coupling between stark levels of 4I13/2 (Er3+). Three independent modes show distinct thermometric performance in different NIR transparency windows and temperature ranges, and the combination of the three modes is conducive to obtain more accurate temperature readings in a broad temperature range, which paves the way toward versatile luminescent thermometers.

Optical spectral study of Nd3+ in YSZs with ion beam-induced luminescence

Ion beam-induced luminescence (IBIL) spectroscopy based on the stark level characteristics of trivalent neodymium (Nd3+): 4F3/2 → 4I9/2 emissions is a powerful tool for characterizing material molecules and crystal structures and quantifying radiation damage. Its spectral parameters are considered to characterize the molecular and crystal structure environment and to track the degree of short-range order disturbance of cationic sites. However, IBIL-based related technologies have rarely been reported. In this article, the IBIL of Nd3+ in yttria-stabilized zirconia (YSZs) was studied in the near-infrared region, especially the Nd3+: 4F3/2 → 4I9/2 emission at room temperature with 2 MeV H+. The results show that 1) a single IBIL spectrum carries as much information about the structure of a substance as the PL spectrum. 2) The surrounding crystal environments of Nd3+ cations in the three samples are consistent. 3) H+ does little damage to the sample in the course of analysis.

Insight into the spectroscopic and thermometric properties of titanate phosphors via a novel co-excited laser system

An approach to enhance the photophysical properties of Er3+-Nd3+-Yb3+ codoped CaTiO3 perovskite phosphors synthesized via solid state reaction technique under 808 nm and 980 nm co-excitation has been described. The band gap analysis and Rietveld refinement has been done on the basis of UV–Vis and XRD spectra. Frequency upconversion observed in the developed phosphors has been explained with the help of steady rate equations. Fluorescence intensity ratio (FIR) based temperature sensing study of the developed phosphors for different combination of thermally coupled Stark levels under co-excitation has been analysed over a range of 303–573 K. Consequently, the maximum sensitivity ~10.9 × 10−3 K−1 at room temperature (303 K) with an excellent thermal resolution (~0.4 K) due to Stark splitting thermally coupled (2H11/2(1) &4S3/2(2)) levels in comparison to the conventional 2H11/2 &4S3/2 levels has been reported.

Long-Range Atom–Ion Rydberg Molecule: A Novel Molecular Binding Mechanism

We present a novel binding mechanism where a neutral Rydberg atom and an atomic ion form a molecular bound state at a large internuclear distance. The binding mechanism is based on Stark shifts and level crossings that are induced in the Rydberg atom due to the electric field of the ion. At particular internuclear distances between the Rydberg atom and the ion, potential wells occur that can hold atom–ion molecular bound states. Apart from the binding mechanism, we describe important properties of the long-range atom–ion Rydberg molecule, such as its lifetime and decay paths, its vibrational and rotational structure, and its large dipole moment. Furthermore, we discuss methods of how to produce and detect it. The unusual properties of the long-range atom–ion Rydberg molecule give rise to interesting prospects for studies of wave packet dynamics in engineered potential energy landscapes.

Intra- and inter-configurational electronic transitions of Ce3+-doped Y2SiO5 : Spectroscopy and crystal field analysis

We report on an interpretation of the 4 f → 5 d absorption and fluorescence spectra as well as the previously un-reported intra-4 f transitions between the Stark levels of the 2 F 5/2 and 2 F 7/2 multiplets of the single seven-fold coordinated, C 1 symmetry site for Ce 3+ in Y 2 SiO 5 . Further, We also give the corresponding crystal-field parameters determined by fitting to the observed energy level data and the ground state Zeeman g tensor obtained from previously reported electron paramagnetic resonance (EPR) measurements. Finally we present a temperature-dependent analysis of the linewidth and position of the 4 f → 4 f absorption lines. • High-resolution infrared absorption measurements for Y 2 SiO 5 :Ce 3+ . • UV fluorescence and absorption spectroscopy of Y 2 SiO 5 :Ce 3+ . • Crystal-field analysis of 4f 1 and 4f5d 1 electronic energy levels of Y 2 SiO 5 :Ce 3+ . • Temperature-dependent linewidth and line shift analysis of Y 2 SiO 5 :Ce 3+ .

Investigation on Thermal Excitation Mechanism of Er^(3+)-doped BaY_2F_8 Single Crystal

The absorption and emission spectra of thermal coupling levels in Er^(3+)-doped BaY_2F_8 single crystal were measured at room temperature (297 K). The effect of temperature on emission spectra was investigated in the range of 12‐297 K. The results show that the intensities of ^4S_(3/2)→^4I_(15/2) (540 nm, 542 nm, 544 nm, 551 nm and 560 nm) Stark level transitions decrease with increasing temperature, while the ^2H_(11/2)→^4I_(15/2) (517 nm, 522 nm, 526 nm and 529 nm) Stark level transitions exhibits the opposite behavior. The thermal excitation mechanism of the Er^(3+) thermal coupling levels will be discussed.

Temperature-dependent radiative lifetime of Yb:YLF: refined cross sections and potential for laser cooling

We revisit the spectroscopic characterization of ytterbium-doped LiYF4 (Yb:YLF) for the application of laser cooling. Time-dependent fluorescence spectroscopy reveals a temperature dependence of the radiative lifetime which we explain by the Boltzmann distribution of excited ions in the upper Stark levels. The emission cross sections of Yb:YLF from 17 K to 440 K are revised using the temperature-dependent radiative lifetimes from fluorescence spectra. We provide fit equations for the peak values of important transitions as a function of temperature, which is also useful for the design of Yb:YLF laser oscillators and amplifiers operated at cryogenic temperatures. Based on our spectroscopic data, we show the prerequisite crystal purity to achieve laser cooling below liquid nitrogen temperatures.

Synthesis and Investigation of Magnesium–Aluminum Nanopowders and Ceramics Activated by Copper

Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt %), and cuprite (2 wt %) have been obtained by laser evaporation of a solid target, which is a mechanical mixture of simple oxides (MgO, Al2O3, CuO). These nanopowders have been used to prepare test samples of transparent Cu:MgAl2O4 ceramics, the IR transmission spectra of which revealed two new strong absorption bands at λ1 ≈ 1.55 (1.45) μm and λ2 ≈ 3.45 (3.03) μm, corresponding to transitions between the Stark levels 2E( $${\text{t}}_{2}^{6}$$ e3) and 2T2 ( $${\text{t}}_{2}^{5}$$ e4) of Cu2+ ions in octahedral and tetrahedral positions, respectively.

Crystal field module for the general relativistic atomic structure package

The latest version of the grasp2018 package [Froese Fischer et al. (2019)], based on the multiconfigurational Dirac–Hartree–Fock method, is extended to account for effects of crystal fields in complex systems. Instead of using the simplified treatment of the crystal field effects based on the Stevens’ operator-equivalent method the program uses the fully ab-initio method in which the external ions are treated as point charges at fixed positions. In addition, examples of how to use the CF_Hamiltonian program are given in source directory grasp2018/src/appl/CF_Hamiltonian/Sample_Runs. Program summaryProgram Title:CF_HamiltonianCPC Library link to program files:https://doi.org/10.17632/fksxwwjbx6.1Licensing provisions: MIT licenseProgramming language: Fortran 95.External routines/libraries used:Grasp2018 modules: Libmod, Lib9290, Librang90; Grasp2018 routines: starttime, setdbg, getmixblock, getmixa, getmixc, setmc, factt, setcon, setcsla, stoptime; and Lapack library.Nature of problem: The CF_Hamiltonian program is designed as a part of the Grasp2018 package for the computation of Stark splitting in crystal field in the point charge crystal field approximation.Solution method: The point charge crystal field approach is used. It allows user to include different Atomic State Functions (ASF) mixing such as ASF mix with the same total J values, ASF mixing with different total J values, ASF mixing with different parities.Additional comments including restrictions and unusual features: The restrictions of the program are coming from the restrictions of Grasp2018 package and it is suitable for systems for which the point charge crystal field approximation is appropriate. The Stark level splitting of the atomic energy terms in the point-charge crystal field approach is performed by the program CF_Hamiltonian.

Erbium energy levels in GaN grown by hydride vapor phase epitaxy

Erbium doped GaN (Er:GaN) is a promising candidate as a novel gain medium for solid-state high energy lasers (HELs) due to its superior physical properties over a synthetic garnet such as Nd:YAG. Er:GaN emits in the 1.5 µm region, which is retina-safe and has a high transmission in the air. We report photoluminescence (PL) studies performed on Er:GaN epilayers synthesized by the hydride vapor phase epitaxy (HVPE) technique. The room temperature PL spectra of HVPE grown Er:GaN epilayers resolved as many as 11 and seven emission lines in the 1.5 µm and 1.0 µm wavelength regions, respectively, corresponding to the intra-4f shell transitions between Stark levels from the first (4I13/2) and the second (4I11/2) excited states to the ground state (4I15/2) of Er3+ in GaN. The observed peak positions of these transitions enabled the construction of the detailed energy levels in Er:GaN. The results agree well with those of the calculation based on a crystal field analysis. Precise determination of the detailed energy levels of the Stark levels in the 4I11/2, 4I13/2, and 4I15/5 states is critically important for the realization of HELs based on Er:GaN.

Effect of Rb+ Doping on Tunable Luminescence in Yb3+/Er3+–Y2O3 Film

In this paper, a series of Rb+-doped Er3+/Yb3+–Y2O3 films were synthesized via a sol-gel method and spin coating. The structure and morphology of the samples were investigated by X-ray diffraction and scanning electron microscopy. The Rb+-doped films with nanoparticles, in the size range of 20–40 nm, were obtained. The spectroscopic analysis of the samples was investigated by using the emission spectra and the intensity of luminescence. All the samples exhibited a green emission ascribed to 2H11/2/4S3/2 to 4I15/2 of Er3+ and a red one ascribed to 4F9/2 and its stark level to 4I15/2 of Er3+. As the Rb+ concentration increased, the intensities of the green light and red light were enhanced 16.97- and 5.81-fold relative to that of the undoped sample. Moreover, by controlling the Rb+ concentration, the samples were capable of generating color-tunable luminescence from red to green linearly. The tunable emission was caused by the change of ion distribution ratio in 4F7/2(Er) and 4F9/2(Er) levels. The results suggest that the as-prepared Rb+-doped Er3+/Yb3+–Y2O3 films have a great potential for applications of luminescence.

Luminescent Nd3+‐Based Microresonators Working as Optical Vacuum Sensors

AbstractGlass microspheres embedded with Nd3+‐doped nanoperovskites based on yttrium orthoaluminate are synthesized and used as optical vacuum sensor. Under 532 nm excitation, the microspheres show two emission bands centered at 820 and 890 nm, corresponding to the 2H9/2,4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions. When the microspheres are heated by laser excitation in air (ambient conditions), the positions of the Stark level transitions shift toward red or blue spectral regions. Additionally, the full width at half maximum of these peaks increases. Furthermore, due to the specific geometry of the microspheres, it is possible to trap the emitted light inside the microsphere resonator, in the form of whispering‐gallery‐modes (WGM). When the microspheres are heated, these resonant modes present higher shifts toward lower energies than those for the Stark levels. As pressure decreases, the thermal exchange (convection process) between the microsphere and the surrounding air molecules decreases, which leads to an increase on the temperature of the microsphere. Based on this effect, the response of the WGM spectral positions as a function of pressure level is used to calibrate the luminescent microspheres as optical vacuum sensors. Relative sensitivity and limit of detection are obtained and compared with other optical vacuum sensors.

Er3+, Yb3+ co-doped Sr3(PO4)2 phosphors: A ratiometric luminescence thermometer based on Stark levels with tunable sensitivity

Novel precise thermometers are increasingly important due to the development of electronic and optoelectronic devices. Up-converting Sr3(PO4)2:Er3+,Yb3+ phosphor, exhibiting anti-Stokes luminescence has been developed as an optical temperature sensor. The basic physicochemical properties of the synthesized material, i.e. crystal structure, morphology, diffuse reflectance spectrum, up-conversion (UC) emission and the corresponding chromaticity diagram were systematically studied. The UC luminescence properties of the micron-sized particles synthesized are strongly temperature-dependent, from 303 to 623 K. By using a single material, the selection of different Stark sublevels results in various temperature sensitivities. Using band intensity ratio of Er3+ Stark components 2H11/2(1)/4S3/2(1), the relative sensitivity of 0.88% K−1 at 303 K was obtained.

Atomistic simulation and spectroscopic study of the [formula omitted] doped [formula omitted] crystal

The CaSO4:Eu3+ has been prepared by the slow evaporation route with different concentrations of the luminescent ion, characterized by XRD and emission spectra techniques and studied by atomistic simulation and crystal field theory. The lattice parameters were obtained with a new set of potentials which is proving to be more appropriate to simulate the lattice parameters and the local Eu3+ luminescent site than those published elsewhere. The Simple Overlap Model (SOM) was applied in the frame of the Method of Equivalent Nearest Neighbours (MENN) in order to predict the charge factors devoted do the Eu–O bond and the 7F1 energy sub-levels through the crystal field parameters. The central ion charge (gEu) was predicted by the Batista–Longo Improved Model (BLIM). Our calculations indicated that the Eu3+ prefers the Ca2+ site compensated by calcium vacancy or interstitial oxygen. Using the four simulated structures the 7F1 Stark levels were satisfactory reproduced. Thus, based on the simulations and the number of lines exhibited in the emission spectra, one has a strong indication that the Eu ion occupies a distorted local symmetry which is a combination of the D2 and C2v point groups.