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Y10Ta4O25:Eu3+ presents peculiar spectra and excellent red luminescence properties due to its special fluorite-related structure. The microstructure was characterized by the site-selective luminescence of Eu3+ activators.

Tungsten bronze-type ceramics have been widely investigated as one of the best ferroelectric frameworks. RE-doped Ba2NaNb5O15 phosphors have been reported with unsatisfactory luminescence efficiencies. It is attractive to develop a ferroelectric showing multifunctionality with electric and luminescence performances. In this work, the cation substitutions of (Eu3+ → Ba2+) and (Ti4+ → Nb5+) are realized in tungsten bronze-type Ba2NaNb5O15 to develop optoelectronic ceramics (luminescence + dielectric). The introduction of framework-disturbances is regarded to be an effective strategy on modification of the luminescence and electronic properties. The ceramics were prepared using the high-temperature solid-state reaction. The cation disorder due to Eu3+/Ti4+ co-doping can significantly enhance the luminescence efficiency and thermal stability. Meanwhile, Eu3+/Ti4+ co-doping has a strong influence on the microwave dielectric performances, that is, the dielectric constant (er) values and quality factor (Q × f) were significantly improved. The temperature coefficient of resonant frequency (τf) is optimized. The improvement of optoelectronic effects shows a significant dependence on cation disorder of the ferroelectric framework.

In this work, a series of mixed pyrophosphates (Mg1-xMnx)2P2O7 (x = 0-1.0) were prepared for the first time using a solid-state reaction method, which exhibits two kinds of structural variants, that is, α-(low temperature) and β-(high temperature) phases. The detailed phase-formations were determined via structural Rietveld refinements and the luminescence transitions of 4T1 → 6A1 in Mn2+. The phase-formation of (Mg1-xMnx)2P2O7 (x = 0-1.0) shows a strict dependence on Mn2+ doping contents in the lattices. (Mg1-xMnx)2P2O7 has an α-Mg2P2O7 phase when the Mn2+-doping concentration is lower than x ≤ 0.1. With an increase of Mn2+ substitution above 20 mol% (x = 0.2-1.0), (Mg1-xMnx)2P2O7 presents only the β-phase even at room temperature, while (Mg1-xMnx)2P2O7 (x = 0.15) shows a mixed formation of α- and β-Mg2P2O7 phases. The crystallographic surrounding of the Mn2+ activators in different structures had a strict influence on the spectral profile, luminescence efficiency, and color centers. Interestingly, in this series of phosphors, (Mg1-xMnx)2P2O7 (x = 0.15) with the mixed phases of α- and β-type has overwhelming luminescence abilities such as the best luminescence intensity and high thermal stability. The pyrophosphates were confirmed to qualify for red-emitting LED lamps.

BiVO4 was selected as a model to manipulate the luminescence and photocatalysis by Eu3+ ions incorporation. Eu3+-uniformly doped and surface-localized BiVO4 was prepared by a coprecipitation route ...

Bismuth niobate semiconductors are of considerable interest in both contaminant degradation and H2-generation. However, the wide band gap strictly limits the optical absorption in visible-light wavelength. In this work, a new niobate semiconductor Bi3Nb17O47 was prepared with co-precipitation synthesis. To modify the band structure, Te4+-, Ti4+-, and Te4+/Ti4+-doping were conducted in Bi3Nb17O47 lattices. Rietveld refinements were used to investigate the crystal phase and structure. The UV–vis absorption measurements concluded that Te4+-, Ti4+- doping could greatly modify the band energy of Bi3Nb17O47. The Te4+/Ti4+-doped sample could harvest more visible light in the longer-wavelength region being favorable for photocatalysis performances. This was verified by RhB photodegradation tests under the visible-light irradiation (λ > 420 nm). To discuss the photocatalytic mechanisms, XPS and impedance spectra were measured. The improved photocatalysis was related to the microstructure changes, charge carrier dynamics, oxygen vacancies, and redox couples of multivalent ions. The present work provides a valid route to modify the band structure and to improve the photocatalysis abilities via impurity ions Te4+/Ti4+-doping in bismuth niobate semiconductors.

The Bi3+-containing semiconductors have been widely reported as potential photocatalyst candidates for water-splitting and environmental pollution problems. This work reported a new kind Bi-heterojunction of LiBiO2/Bi2O3, which was synthesized by the facile hydrothermal reactions. The XRD (X-Ray powder diffraction) measurement was applied to investigate the phase formations. The composite crystals developed in the well-crystallized ultrathin nanosheets with the thickness about 320 nm. The UV–visible absorption indicated that LiBiO2/Bi2O3 heterojunction has a similar optical absorption edge to that of LiBiO2 (2.04 eV). This confirms the heterojunction has the actively optical abilities in visible wavelength region. The photocatalytic activities were tested by photo-degradation effects of rhodamine B (RhB) dye and colorless phenol solutions under the visible light irradiation. The experiments suggested that the photocatalysis activities could be greatly improved via coupling Bi2O3 in LiBiO2/Bi2O3 heterojunctions. The migration of light-induced charge-carriers adopts a typical direct Z-scheme in LiBiO2 and LiBiO2/Bi2O3 heterojunctions.

Here we show an innovative way to effectively scavenge highly mobile radioiodide and to dramatically reduce its waste volume through a spontaneous phase transformation. Under an anaerobic condition, as metallic copper (II) was favorably associated with bicarbonate (HCO3−) in solution, a cupriferous carbonate compound (malachite) quickly formed, which was redox-sensitive and transformable to a compact crystal of CuI (marshite). The formation of CuI crystal was principally led by the spontaneous Cu–I redox reaction centering around the copper phase over the presence of sulfate (SO42−). The completely transformed CuI crystal was poorly soluble in water and grew to large microcrystals (∼μm) via a remarkable selectivity for I−. Interestingly, this redox-induced iodide crystallization was rather promoted over the existence of anionic competitors (e.g., HCO3− and SO42−), which usually exist in wastewater and natural water. Unlike the conventional methods, these competing anions positively behaved in our system by supporting that the initial malachite was more apt to be reactive to largely attract highly mobile I−. Under practical environments with various anions, such a selective I− uptake and fixation within a compact crystalline space will be a promising way to effectively remove I− in a great capacity.

Aluminosilicate with the cordierite structure (Mg2Al4Si5O18) represents a big family of technologically important compounds with typical α- and β-phases. Crystallographic sites for transition metal and rare earth ions in the cordierite structure have always been a controversial topic. In this work, the (Mg1−xMnx)2Al4Si5O18 (x = 0–1.0) solid solution is firstly confirmed via Rietveld structural refinements and luminescence dynamics. The well-crystallized ceramics were prepared by high-temperature solid-state reaction, and then characterized using structural, morphological, luminescence, decays, and thermal quenching measurements. (Mg1−xMnx)2Al4Si5O18 (x = 0–1.0) undergoes structural changes from the orthorhombic β-phase (x = 0–0.2), α-phase (x = 0.3–0.9) and Mn-cordierite (x = 0.95–1.0) (isostructural to β-phase). It is technically meaningful that high-temperature α-phase cordierite Mg2Al4Si5O18 can be stabilized via Mn2+-doping (30–90 mol%). The crystallographic site-occupation of Mn2+ activators is clearly identified. Interestingly, (Mg1−xMnx)2Al4Si5O18 (x = 0.01–1.0) presents tunable colors produced by two distinct luminescence centers, that is, green Mn2+(A) and red Mn2+(B) bands centered at about 530 and 650 nm, respectively. The most efficient excitation wavelengths and decay times of Mn2+(A) are distinct from those of Mn2+(B). The Mn2+(A) green centers are only observed in β-phase cordierite (x = 0.01–0.2) with a dominant emission intensity compared with Mn2+(B), while the Mn2+(B) red centers are observed in all samples (x = 0.01–1.0). The Mn2+(A) center fills in the hexagonal channels, while Mn2+(B) is related to the substitution of Mn2+ for the octahedral Mg2+ site in the cordierite lattices. The luminescence mechanism of Mn2+ in (Mg1−xMnx)2Al4Si5O18 was proposed. The results can be used for basic and application research studies in a wide family of rare earth or transition-metal-doped cordierite materials.

There is a close correlation between the photoluminescence and photocatalysis of a semiconductor because the two processes involve the same electronic transition. Eu3+ is one of the most popular rare-earth ions; it presents efficient luminescence and improved photocatalysis. Usually, the luminescence from the higher states (5D1,2) of Eu3+ can be hardly observed due to cross-relaxation processes. This work demonstrates a particularly developed transition from the 5D1 level of Eu3+ and its significant contribution to the improved photocatalysis of (Bi3Li)O4Cl2via prolonging the decay time of the excited state. Single-phase (Bi3−3xEu3xLi)O4Cl2 (x = 0, 0.01, 0.03, 0.05) was synthesized by the sol–gel method in combination with a solid-state reaction. This is a bismuth layer structure with [(Bi/Li)O2]2+ layers formed by alternative Bi3+ and Li+ stripes. The intrinsic luminescence of (Bi3Li)O4Cl2 (λem = 500 nm) with a decay time of 0.26 μs was detected even at 300 K. Unusually, the phosphor shows a prominent transition from 5D1 in (Bi3−3xEu3xLi)O4Cl2. Moreover, in addition to 5D0 → 7F3, 5D0 → 7FJ (J = 0, 1, 2, 4) is characterized by intense transitions with comparable intensities. The intrinsic emission of (Bi3Li)O4Cl2 has a decay time which involves the band transition of an electron from the valence band to the conduction band. In Eu3+-doped (Bi3Li)O4Cl2, there are midgap states formed by the 5D1 level with a longer lifetime of about 60 μs. The D1 levels of Eu3+ significantly contribute to the separation of light-induced charges by prolonging the decay time of the excited states. This work demonstrates a simple strategy to develop optical materials with simultaneous luminescence and has improved the photocatalysis in bismuth oxychlorides featuring strong polarization and rigid phonons.

Luminescence properties of the Cr3+-doped LiGaW2O8 crystals are investigated by laser excitation spectroscopy. The powder samples for various Cr3+ concentration were prepared by high-temperature solid state reaction. The temperature behaviors of the emission intensity and the decay time of the self-activated LiGaW2O8 host are discussed. The emission spectra and decay times of LiGa1-xW2O8:xCr3+ are measured under UV excitation in the temperature range 10–300 K. The luminescence quenching of LiGaW2O8:Cr3+ as functions of temperature and Cr3+-concentration is explained by structural and spectral characteristics.

Ce3+, Tb3+ and Ce3+-Tb3+ activated Ba3Y2(B2O5)3 phosphors were synthesized by a sol-gel pyrolysis method. The synthesized phosphors were investigated using X-ray diffraction (XRD) analysis, photoluminescence emission and excitation spectra and luminescence decay curves. In the Ce3+ activated Ba3Y2(B2O5)3 samples, two different Ce3+ centers (marked as Ce(1) and Ce(2)) could exist. The Ba3Y2(B2O5)3:Tb3+ phosphor shows some emission peaks at ∼350–650 nm among which the green emission peak at 540 nm is the strongest. For the Ba3Y2(B2O5)3:Ce3+, Tb3+ co-doped phosphor, the existence of energy transfer process from Ce3+ center to Tb3+ center is confirmed and the interaction mechanism between Ce3+ and Tb3+ in Ba3Y2(B2O5)3:Ce3+,Tb3+ system is dipole-dipole interaction based on Inokuti–Hirayama (I H) model.

Cs-doped α-Bi2O3 was synthesized via a facile hydrothermal reaction. The phase formations of the samples were investigated via X-ray powder diffraction (XRD) patterns and structural refinements. The samples present well-crystalized microplates with smooth surfaces and a thickness about 300 nm. The experiments revealed that the undoped and Cs-doped α-Bi2O3 microplates could crystallized in a pure monoclinic phase. The band gap of α-Bi2O3 could be reduced via the Cs-doping in the lattices. The photocatalytic activity on photo-degradation of methylene blue (MB) was significantly improved with the Cs-doping. The effective photocatalysis was discussed on the improved visible-light response, the enhanced dispersion in the valence band composed of hybrid orbitals of Bi6s, O2p and Cs3d, and the lowered electron–hole recombination.

Gd8V2O17 was prepared via the facile solid-state reaction. The optical absorption, temperature-dependent luminescence, and decay lifetimes were investigated. Gd8V2O17 has a direct allowed electronic transition with band gap energy of 3.18 eV. Under the excitation of UV light, the phosphor shows the typical self-activated luminescence from the charge transfer (CT) transitions in VO43− groups. The emission intensity has a nearly constant value from 10 to 150 K, while it increases above 150 K. And the emission has an abnormal blue-shift with the increase of temperature from 10 to 300 K, so the luminescence color varies from green to blue. Over the whole temperature ranges, the maximum emission wavelength showed a linear dependence on temperature; consequently, the temperature-dependent properties have a potential advantage in luminescence thermometry. The luminescence mechanism was discussed on the proposed two VO4 emission centers and the energy transfer between them.

Photoluminescence properties of CaS:Cu+, CaS:Mn2+ and CaS:Cu+, Mn2+ rare-earth -free phosphors prepared by a carbon-thermal reduction method were investigated. The emission spectrum of Cu+-doped CaS consists of two overlapped bands peaking at 415 nm (attributed to isolated Cu+ activator) and 475 nm (attributed to aggregated Cu+ center). The influence of Cu+ doping concentration on the emission spectrum is discussed. The emission spectrum of Mn2+-doped CaS exhibits a band emission peaking at 568 nm under 250 nm excitation. The emission spectra of the doubly activated CaS:Cu+, Mn2+ phosphors consist of Cu+ and Mn2+ emissions simultaneously, and their shapes depend strongly on the Mn2+ concentration. Based on the emission and excitation spectra of the CaS:0.15 mol%Cu+, xMn2+ phosphors, the energy transfer from Cu+ to Mn2+ takes place. The emitting colors of the doubly activated phosphors can also be tuned. In particular, the emitting color of CaS:0.15 mol% Cu+, 0.6 mol % Mn2+ sample is close to white light.

In the present study, BiNb5O14 and BiNb5O14/Nb2O5 heterojunction were prepared with co-precipitation synthesis. The crystal structure was studied via XRD patterns and Rietveld refinements, which has a typical tetragonal tungsten bronze (TTB)-type structure. The samples crystallized in micorods with a length of 1–4 µm and a diameter about 1 µm. As an indirect transition semiconductor, BiNb5O14 has a band energy of 2.81 eV with the valence-band formed by hybridized O-2p and Bi-6s, and the conduction band formed by Nb(6d) orbitals. The photocatalysis abilities of BiNb5O14 and BiNb5O14/Nb2O5 heterojunctions were evaluated via the photo-degradation of dye solutions. The photocatalytic activities were significantly improved via coupling BiNb5O14 with Nb2O5. In the photocatalysis reactions, •OH was the main reactive species, and the immigration rate of light-created charge-carriers was greatly improved via the heterojunction structure. The luminescence and decay lifetime were measured to discuss the photocatalysis mechanism.

In this work, a series of mixed pyrophosphates (Mg1-xMnx)2P2O7 (x = 0-1.0) were prepared for the first time using a solid-state reaction method, which exhibits two kinds of structural variants, that is, α-(low temperature) and β-(high temperature) phases. The detailed phase-formations were determined via structural Rietveld refinements and the luminescence transitions of 4T1 → 6A1 in Mn2+. The phase-formation of (Mg1-xMnx)2P2O7 (x = 0-1.0) shows a strict dependence on Mn2+ doping contents in the lattices. (Mg1-xMnx)2P2O7 has an α-Mg2P2O7 phase when the Mn2+-doping concentration is lower than x ≤ 0.1. With an increase of Mn2+ substitution above 20 mol% (x = 0.2-1.0), (Mg1-xMnx)2P2O7 presents only the β-phase even at room temperature, while (Mg1-xMnx)2P2O7 (x = 0.15) shows a mixed formation of α- and β-Mg2P2O7 phases. The crystallographic surrounding of the Mn2+ activators in different structures had a strict influence on the spectral profile, luminescence efficiency, and color centers. Interestingly, in this series of phosphors, (Mg1-xMnx)2P2O7 (x = 0.15) with the mixed phases of α- and β-type has overwhelming luminescence abilities such as the best luminescence intensity and high thermal stability. The pyrophosphates were confirmed to qualify for red-emitting LED lamps.

We have developed the PolCube payload, a polarimeter camera for 12U CubeSat mission, in order to demonstrate the performance feasibility technically since 2019. Main objectives of the PolCube camera are the dust detection around Korean peninsula and monitoring super-thin clouds distribution on global oceans. KASI and Korean consortium members maintain a good collaboration with NASA LaRC team in this project. PolCube is a compact payload under 5kg in mass and under 15W in power consumption. This payload has two optical heads, two detectors with 1280 x 1024 CMOS array format, and two filter sets with 4 wavelengths and 0, 60, 90, 120 polarization angles. Each optical head has a field of view of 10 degrees (Swath width ~ 98km) at the altitude of 567km Sun-synchronous orbit. 12U CubeSat spacecraft will be made by a CubeSat company managed by Busan city & KIOST in Korea. In this paper, we will describe the current design of the PolCube payload development.

CaB

Molybdenum and vanadium mixed oxides of Mo6V9O40 and Mo6V8.5Te0.5O40 were synthesized by the modified sol-gel method. The phase formation and structure were investigated through X-ray powder diffraction (XRD) patterns. The optical absorption measurements show that the sample has an efficient light response covering the region UV-visible to near IR wavelength. The two Mo-V mixed oxides of Mo6V9O40 and Mo6V8.5Te0.5O40 show an indirect forbidden transition with band energies of 1.67 eV and 1.64 eV, respectively. The multivalent cations (V and Mo ions) were confirmed via X-ray photoelectron spectroscopy (XPS) measurements. The effective photocatalysis of the samples was conducted via the photodegradation of RhB under visible-light irradiation (λ≥420 nm). The conductivity properties and lifetime of charge carriers were characterized via impedance spectra and luminescence decay curves respectively. It was suggested that intrinsic redox couples in these Mo-V mixed oxides lead to intervalence transfer between V5+/4+ and Mo6+/5+ couples, which can improve photocatalysis. This work offers a potential alternative material with rich intrinsic redox couples and defects toward high-performance photocatalyst.

Optical thermometry based on the adjacent thermally coupled levels of rare earth ions has been widely studied in the high temperature range, and shows unobvious effect at low temperature range. In this work, we propose a new method to achieve optical thermometry in 10˜300 K range through manipulating the energy transfer from WO66− to Ho3+. A comprehensive five-level rate-equation model is developed to establish the relation between lifetime ratios and temperature. It is found that the lifetime ratios of 540 nm (Ho3+) and 471 nm (WO66−) emissions are dependent on the phonon energy of Y2WO6 host and temperature. The values of sensor sensitivity reach the maximum 2.1% K−1 at 211 K in 30%Ho3+ doped Y2WO6, which is higher than the maximum of the reported phosphors at low temperature. It overcomes the shortcoming of unobvious thermal population of thermally coupled levels in low temperature range through traditional Boltzmann distributing method.

We present an optical pressure sensor KMgF3:Eu2+ suitable for experiments in diamond anvil cell (DAC), which we have calibrated against the ruby reference sensor at pressures ranging from atmospheric up to 30 GPa (300 kbar), at room temperature. The emission spectra of KMgF3:Eu2+ consist of one prominent emission line related to the 6P7/2 → 8S7/2 electronic transition (zero phonon line) accompanied by weak phonon sidebands. The energy of emission at atmospheric pressure was determined to be 27846 ± 7 cm−1. The edge of the excitation spectrum lies at wavelength around 325 nm (30800 cm−1) making it suitable to excite with He-Cd laser (325 nm). The sensor exhibits linear pressure shift of rate equal to −0.815 ± 0.007 cm−1/kbar at pressures up to 300 kbar. The pressure shift of the emission is totally reversible and the pressure sensor is suitable for multi cycle pressure experiments. The sensor's exceptional feature is that excitation and emission spectra lie in near UV, which makes it very convenient to use in high pressure optical measurements in visible and IR region with no interference from the sensor's luminescence.

Luminescence properties of sodalite Zn4B6O13:Mn2+ are investigated by optical and laser excitation spectroscopy in the temperature range 10 – 300 K. The samples of Zn4B6O13:Mn2+ are prepared in the carbon reducing atmosphere. The green emission at 540 nm are observed in Zn4B6O13:Mn2+ for various Mn2+ concentration. Optimum Mn2+ concentration and critical distances between Mn2+ ions in Zn4B6O13 are obtained by the luminescence intensity as functions of Mn2+ concentration. The decays of Mn2+ emission depend strongly on Mn2+ concentration due to the energy transfer and energy diffusion in Zn4B6O13:Mn2+. The fine structures consisting of the intense zero phonon line (ZPL) and weak vibrational sidebands are observed at low temperature. The relevant mechanism of excitation bands, ZPL, vibrational sidebands and the bandwidth as functions of temperature are interpreted in detail by energy level diagram of the 3d5 transition metal ions and configuration coordinated diagram. The high thermal stability of the Zn4B6O13:Mn2+ phosphor are observed in the temperature range 10–300 K.

Ce3+, Tb3+ co-doped T-phase orthosilicate Ba1.2Ca0.8SiO4 phosphors were prepared by means of solid state reactions. The synthesized samples were investigated using XRD and PL emission and excitation spectra. The emission spectra for Ce3+ doped Ba1.2Ca0.8SiO4 phosphors show broad bands in the 320–550 nm spectral region. The excitation spectra exhibit several absorption peaks in the range of 250–400 nm. Both the emission and excitation spectra are dependent on the excitation or monitoring wavelengths. We attribute these results to Ce3+ ions occupying two different crystallographic sites (i.e., Ce I and Ce II). The Ce3+, Tb3+ co-doped Ba1.2Ca0.8SiO4 phosphors show Tb3+-related line emissions in the 475–600 nm spectral region and Ce3+-related band emissions in the 350–525 nm spectral region when the 4f → 5d transition of Ce3+ is excited (λex = 345 nm), indicating that energy transfer from Ce3+ to Tb3+ takes place. Moreover, the emission intensity of 5D4 → 7F5 transition for Ba1.00Ce0.02Tb0.08Li0.10Ca0.8SiO4 is 30 times stronger than that of Ba1.04Tb0.08Li0.08Ca0.8SiO4 sample under 345-nm UV excitation.

Pure and V-doped NiTiO3 (NiTiO3:V) nanorods were synthesized via electrospinning synthesis using sol–gel precursors, followed by sintering the samples at 600 °C. And the subsequent Ag-loaded NiTiO3:V nanorods were prepared by the chemical precipitation method (Ag/NiTiO3:V). The phase formations were studied via X-ray powder diffraction (XRD) measurements. The Rietveld refinements were conducted to investigate the structural characteristics. The surface property of the nanorods was measured via morphologies and X-ray photon spectrascope (XPS) measurements. The absorption spectra of products indicate sufficient optical response in visible wavelength region. The indirect allowed band gap (2.18 eV) of NiTiO3 originates from the characteristic charge-transfer (CT) transitions of O2− → Ti4+ (UV region) and Ni2+ → Ti4+ (visible light region). While Ag/NiTiO3:V composites have a smaller band energy of 2.09 eV. The photocatalytic activities were investigated by photo-degradation of Rhodamine B (RhB) dye solutions under visible-light irradiation. The Ag/NiTiO3:V nanorods were efficient for the photo-degradation of RhB dye solutions. EIS measurements were used to analyze the charge-carrier migration at the interfaces. The improved photocatalysis of Ag/NiTiO3:V is ascribed to the narrowed band energy and enhanced efficiencies of the charge separations due to the Ag-coupling and V-doping in NiTiO3 lattices.

The Y2WO6:Yb3+/Er3+ crystals were synthesized by the hydrothermal method. The needle-shaped morphology is controllably formed and a number of crystals aggregate as spheres by adding the surfactant of sodium dodecylbenzenesulfonate (SDBS) into the reaction system. The crystal structure, morphology and upconversion luminescence properties of the Y2WO6:Yb3+/Er3+ crystals are conducted on the basis of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), FTIR and emission spectra. The different emission intensity ratio of the red and green bands is observed for the Y2WO6:Yb3+/Er3+ precursors under different heat treatments. The different intensity ratio are illustrated according to the upconversion mechanism.

Luminescence properties of impurity-trapped excitons (ITEs) in LiBaF3:Eu2+ crystals are investigated by optical and time-resolved laser-excitation spectroscopy. The three excited states of 4f65d, 4f7(6P7/2) and ITE are identified in the excitation and emission spectra. The intensity of ITEs’ emission increases unexpectedly with increasing temperature and excitation energy. The initial intensity of the ITE emission just after pulsed-laser excitation increases continuously with temperature in the temperature range 7–600 K. The results are discussed in relation to radiative and nonradiative rates and excitonic processes in this system. The theoretical model that includes the ITE, 4f7(6P7/2) and 4f6(7FJ)5d(eg) states is developed to describe and support the experimental observations.