scholarly journals SPECTROSCOPIC STUDY OF SALT MELTS OF THE SmF3-CeF3-NaCl-KCl SYSTEM

2021 ◽  
Vol 26 (1(77)) ◽  
pp. 26-36
Author(s):  
V. F. Zinchenko ◽  
O. G. Ieriomin ◽  
I. V. Stoianova ◽  
G. V. Volchak ◽  
N. O. Chivireva ◽  
...  
Keyword(s):  
Solid Phase ◽  
Electronic Transitions ◽  
Luminescence Spectroscopy ◽  
Luminescence Spectra ◽  
Absorption Bands ◽  
Radiation Mechanism ◽  
Complex Fluoride ◽  
Salt Melt ◽  
Exchange Processes ◽  
Ir Transmission

Redox interactions between the components of the SmF3-CeF3 and SmF3-CeF3-NaCl-KCl systems have been established by IR transmission spectroscopy, diffuse reflectance electron spectroscopy and luminescence spectroscopy. A significant decrease in the transparency in the IR range of the spectrum was found when passing from the first of the systems to the second, which is explained by an increase in scattering by ultramicrodispersed particles of fluorides in the salt melt. In both systems, the formation of a significant amount of Sm (II) and a decrease in the content of Sm (III) are observed. The change in the valence state of Samarium both during solid-phase heat treatment (1100 °C) and during holding in a salt melt at 700 °C is manifested in the disappearance of some absorption bands, the appearance of new bands, and a gypsochromic shift of the remaining bands. The luminescence spectra exhibit high-intensity emission bands in the 640–740 nm range, which correspond to 5d‑4f electronic transitions in Sm2+ ions. At the same time, the highest intensity is observed in the band corresponding to intracenter 5d‑4f electronic transitions in Ce3+ ions. Apparently, the Ce(IV) compound, formed as a result of the exchange reaction of complex fluoride with a salt melt, volatilizes with subsequent decomposition and does not affect the character of luminescence. On the whole, the luminescence intensity after treatment in the molten salt increases by several tens of times, which indicates a significant change in the radiation mechanism. The mechanism of redox reactions in the solid-phase state, as well as exchange processes in the salt melt and after its crystallization, is discussed. A significant role of solvation shells around particles of lanthanide fluorides in luminescence processes is assumed.

scholarly journals SPECTROSCOPIC PROPERTIES OF SOLIDIFIED MELTS OF THE EuF3-CeF3-NaCl-KCl SYSTEM

2020 ◽  
Vol 86 (10) ◽  
pp. 120-128
Author(s):  
Viktor Zinchenko ◽  
Oleg Ieriomin ◽  
Valerii Antonovich ◽  
Nataliia Chivireva ◽  
Iryna Stoianova ◽  
...  
Keyword(s):  
Absorption Band ◽  
Luminescence Band ◽  
Diffuse Reflection ◽  
Bathochromic Shift ◽  
Electronic Transitions ◽  
Luminescence Spectra ◽  
Complete Disappearance ◽  
Diffuse Reflection Spectroscopy ◽  
Exchange Reactions ◽  
Salt Melt

The nature of the interaction in the EuF3-CeF3 system in the process of high-temperature (1050 °C) oxidation - reduction reaction was established by the methods of IR transmission spectroscopy, diffuse reflection spectroscopy and fluorescence spectroscopy. Here is a significant bathochromic shift to 480-485 nm band of blue luminescence of Eu(II) - containing phases, due to the 5d–4f electronic transitions, as well as the manifestation of orange-red luminescence of Eu(III) - containing phases due to 4f–4f electronic transitions in the range of 590–690 nm. There is a bathochromic shift of the IR bandwidth in the spectrum of the solidified salt melt as a result of dissolution of the fluoride system. Diffuse reflection spectra reveal changes in the composition of the phases that dissolve in the salt melt due to exchange reactions. The wide absorption band in the UV range gives way to a negative absorption band consisting of two peaks due to luminescence. The almost complete disappearance of the band of 4f–4f transitions in Eu(III) in the near-IR range of the spectrum is evidence of its entire reduction in the chloride melt to Eu(II). The character of the luminescence spectra of solidified salt melts also changes in comparison with the initial sample of the EuF3-CeF3 system, namely, the luminescence band of Ce3+ ions disappears, and the luminescence band of Eu2+ ions at 430–440 nm becomes narrow and highly intensive. The luminescence band of Eu3+ ions in the orange-red region of the spectrum disappears completely. Thus, Eu2+ ions become dominant in the formation of the spectral picture of the solidified salt melt, which is evidence of the completion of the redox process in the system.

scholarly journals Luminescence in lanthanum-gallium tantalate

2018 ◽  
Vol 4 (3) ◽  
pp. 97-101
Author(s):  
Oleg A. Buzanov ◽  
Nina S. Kozlova ◽  
Nikita A. Siminel ◽  
Evgeniya V. Zabelina
Keyword(s):  
Stokes Shift ◽  
Luminescent Properties ◽  
Luminescence Spectra ◽  
Absorption Bands ◽  
Argon Gas ◽  
Complex Process ◽  
Growth Atmosphere ◽  
Luminescence Peak ◽  
Integral Absorption ◽  
20 Nm

The optical and luminescent properties of undoped La3Ga5.5Ta0.5O14 lanthanum- gallium tantalate crystals grown in different atmospheres of pure argon gas and argon gas with different oxygen percentages have been studied. The optical absorption α(λ) spectra that characterize integral absorption and reflection have been measured in the 250–700 nm region. The spectral absorption functions have been calculated from the measured α(λ) spectra using the Kubelka–Munk formula. Luminescence has been observed in all the test specimens over a wide spectral region (375 to 650 nm) at 95 and 300 K. The luminescence spectra of the test crystals have a fine dispersed pattern represented by low-intensity discrete luminescence peaks. The 95 K luminescence peak maxima are more pronounced and shifted towards shorter wavelengths by ~16 nm (~0.1 eV) relative to the respective room temperature peaks. The crystal growth atmosphere has been demonstrated to largely affect the luminescent properties of the crystals: the higher the oxygen concentration in the growth atmosphere, the lower the luminescence intensity due to concentration quenching, the luminescence peak maxima shifting towards longer wavelengths. The positions of discrete luminescence peaks have been shown to correlate with the main 420 and 480 nm absorption bands with the respective ~20 nm (~0.2 eV) Stokes shift for crystals grown in different atmospheres. The luminescence in lanthanum-gallium tantalate crystals is a complex process involving several luminescence mechanisms.

scholarly journals MATHEMATICAL MODELING OF THE THERMODYNAMIC PROCESS GAS-STEAM BUBBLES

2018 ◽  
Vol 1 (50) ◽  
pp. 220-226
Author(s):  
B. А. Kutnyi ◽  
А. М. Pavlenko
Keyword(s):  
Gas Hydrates ◽  
Solid Phase ◽  
Thermodynamic Process ◽  
Size Change ◽  
Process Gas ◽  
Exchange Processes ◽  
Pressure Steam ◽  
Liquid Heat ◽  
Velocity Pressure ◽  
Contact Liquid

A mathematical model that considers the inertial oscillations and thermodynamic components bubbles in liquid heat exchange processes, heat transfer on the boundary bubbles. Research of the dynamic characteristics of gas-steam bubbles in various size was conducted. After the calculations its temperature, velocity, pressure steam environment inside the bubble in time, graphs bubbles size change graphs were built . It is established that each bubble size has its oscillation frequency. Calculated speed phase transients and found that it is in its maximum during the bubble oscillation. For thermodynamic properties of the surface of contact liquid and gaseous phases defined amount of solid phase formed. The research results can be applied to optimize various of technological processes related to the boil, swelling materials, and the formation of gas hydrates in a fluid cavitation.

scholarly journals Luminescence of uranium(VI) after liquid-liquid extraction from HCl by Aliquat® 336 in n-dodecane:1-decanol by time-resolved laser-induced luminescence spectroscopy

2020 ◽  
Vol 108 (7) ◽  
pp. 527-533 ◽  
Author(s):  
Pascal E. Reiller ◽  
Clarisse Mariet
Keyword(s):  
Organic Phase ◽  
Decay Time ◽  
Specific Interaction ◽  
Intensity Variation ◽  
Pitzer Model ◽  
Luminescence Spectroscopy ◽  
Luminescence Spectra ◽  
Time Resolved ◽  
Crystal Field Effect ◽  
Hcl Concentration

AbstractTo investigate the extraction of uranium(VI) in HCl media by Aliquat® 336 in 1:99 (v:v) 1-decanol:n-dodecane mixture, our objective is to identify the complexe(s) in the organic phase by time-resolved laser-induced luminescence spectroscopy (TRLS). The extraction mechanism is supposed to involve the formation of $[U{O_2}Cl_4^{2 - } \cdot {({R_4}{N^ + })_2}]$ in the organic phase. The occurrence of such a species leads to the presence of the ${\rm{U}}{{\rm{O}}_2}{\rm{Cl}}_4^{2 - }$ species in the organic solution, which luminescence shows particular features. The luminescence spectra and decay time evolutions are obtained in the organic phase as a function of HCl concentration in the aqueous phase (0.5–6 M). The extraction of ${\rm{U}}{{\rm{O}}_2}{\rm{Cl}}_4^{2 - }$ is confirmed by the particular spectrum of uranium(VI) in the organic phase, and the typical splitting of the luminescence bands, due to the crystal field effect, is clearly evidenced. The stoichiometry is verified using luminescence intensity variation as a function of the activity of Cl−, and extraction constants are calculated both using the specific interaction theory and Pitzer model. A decomposition of the spectrum of the extracted complex in the organic phase is also proposed. The decay time variation as a function of temperature allows estimating the activation energy of the luminescence process of the extracted complex.

Structural, electronic and spectroscopic features of the dihydride Pd4(dppm)4(H)22+ cluster catalyst

2001 ◽  
Vol 79 (5-6) ◽  
pp. 552-559 ◽  
Author(s):  
Daniel Meilleur ◽  
Pierre D Harvey
Keyword(s):  
Low Frequency ◽  
Inert Atmosphere ◽  
Electronic Transitions ◽  
Absorption Bands ◽  
Palladium Hydride ◽  
H Nmr ◽  
Significant Difference ◽  
Simple Selection ◽  
Centrosymmetric Structure ◽  
Ft Raman

1H NMR, vibrational, and UV–vis spectroscopic measurements for Pd2(dppm)2Cl2 (dppm = Ph2PCH2PPh2), [Pd4(dppm)4(X)2](BF4)2 (X = Cl, H), and [Pd4(dmpm)4(H)2](Br)2 (dmpm = Me2PCH2PMe2) were performed to address the structure of the recently identified title cluster. Its dmpm analogue was prepared from the reaction between Pd2(dmpm)2Br2 and NaBH4 in methanol under inert atmosphere, and exhibits the expected nonet (rel. int. 1:8:28:56:70:56:28:8:1) at –5.21 ppm (in (CD3)2CO), contrasting with that of Pd4(dppm)4(H)22+ (δ + 5.15 ppm, (CD3)2CO). This significant difference is explained by the presence of the PdH residues in the deshielding region of the dppm-phenyl groups. The vibrational spectra in the low-frequency region are consistent with a centrosymmetric structure, and a scattering at 144 cm–1 in the FT-Raman spectra is observed; a peak that is assigned to ν(Pd2) on the basis of a comparison with the well established M2-bonded Pd2(dppm)2Cl2 data ((Pd2) = 149 cm–1). On the basis of the qualitative temperature behavior of the band maxima and width, the two lowest energy absorption bands in the UV–vis spectra are assigned to d σ [Formula: see text] d σ * type transition. EHMO computations predict four well-isolated frontier MO levels, defined as d σ *(Pd2)/d σ *(PdH) (LUMO + 1), d σ *(Pd2) (LUMO), d σ *(Pd2)/d σ *(PdH) (HOMO), and d σ (Pd2) (HOMO –1), and simple selection rules (u « g) indicate that only two low-energy electronic transitions are orbitally allowed, consistent with the UV–vis findings. Computer modelings show the presence of large cavities above and under the Pd4 plane, described by inner-cavity nonbonded H···H distances of ~5–8 Å.Key words: cluster, palladium, hydride, structure, spectroscopy.

Experimental evidence for trapped exciton states in liquid rare gases

1970 ◽  
Vol 317 (1528) ◽  
pp. 113-131 ◽  
Keyword(s):  
Experimental Evidence ◽  
Absorption Spectra ◽  
Disordered Systems ◽  
Vacuum Ultraviolet ◽  
Solid Phase ◽  
Liquid System ◽  
Rare Gases ◽  
Line Broadening ◽  
Absorption Bands ◽  
Additional Line

In connexion with studies of the electronic structure of disordered systems, we enquire whether there exist exciton states in simple liquids. We report the results of a vacuum ultraviolet spectroscopic study of liquid argon and of liquid krypton doped with xenon. Experimental evidence was obtained for Wannier-Mott type impurity states in liquids which have no parentage in the excited states of the isolated atoms constituting the dense fluid. The absorption spectra of the doped liquid rare gases were monitored in the region 160 to 120 nm. The following experimental results are reported: (a) In the Xe/Ar liquid two absorption bands corresponding to the 1 S 0 → 3 P 1 and to the 1 S 0 → 1 P 1 transitions (or alternatively to the n = 1 Wannier states) were identified at 141 nm (8.80eV)† and at 123nm (10.1 eV). An additional line was observed at 127 nm (9.76eV). (b) In the Xe/Kr liquid three absorption bands were observed at 144.5 nm (8.59 eV), 125.5 nm (9.89 eV) and 129 nm (9.6 eV). (c) The absorption spectra of the doped liquids were compared with the spectra of 1 cm thick doped solid rare-gas crystals. From these results we conclude that: (a) The 127 nm (9.76 eV) band in the Xe/Ar liquid system and the 129 nm (9.61 eV) band in the Xe/Kr liquid system cannot be attributed to a perturbed ‘atomic’ state and are assigned to the n = 2 Wannier state in the liquid. (b) Line broadening of exciton states in the liquid can be accounted for by a simple scattering model. (c) Preliminary information on band gaps in liquid rare gases were obtained from the spectroscopic data. (d) The effect of liquid-solid phase transition on the line broadening of exciton states is consistent with electron mobility data in these systems.

scholarly journals Time- and Temperature-Dependent Luminescence of Manganese Ions in Ceramic Magnesium Aluminum Spinels

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 420
Author(s):  
Nicholas Khaidukov ◽  
Angela Pirri ◽  
Maria Brekhovskikh ◽  
Guido Toci ◽  
Matteo Vannini ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Broad Band ◽  
Solid State Reaction Method ◽  
Luminescence Spectroscopy ◽  
Luminescence Spectra ◽  
Manganese Ions ◽  
Time Resolved ◽  
Synthesis Conditions ◽  
Magnesium Aluminum Spinel

Samples of magnesium aluminum spinel ceramics doped with manganese ions were prepared by a high-temperature solid-state reaction method; their potential as red-emitting phosphors was analyzed using a time-resolved luminescence spectroscopy technique, from room temperature to 10 K. It was found that in the red spectral range, the luminescence spectra of manganese ions in the MgAl2O4 spinel showed a narrow band peaking at 651 nm due to the emission of Mn4+ and a broader emission band in the region of 675 ÷ 720 nm; the ratio of intensities for these bands depends on the synthesis conditions. By applying a special multi-step annealing procedure, the MgAl2O4:Mn4+ phosphor containing only tetravalent manganese ions, Mn4+, was synthesized. Broad-band far-red emission observed from MgAl2O4:Mn and Mg1.25Al1.75O3.75F0.25:Mn phosphors, prepared by a conventional method of a solid-state reaction, was interpreted as coming from Mn3+ ions.

Das Temperaturverhalten der Phosphoreszenz und Fluoreszenz von K3CrF6 / The Temperature Dependence of Phosphorescence and Fluorescence in K3CrF6

1973 ◽  
Vol 28 (7) ◽  
pp. 1131-1135
Author(s):  
E. Koglin
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Crystal Field ◽  
Fluorescence Emission ◽  
Electronic Transitions ◽  
Luminescence Spectra ◽  
Site Symmetry ◽  
Energy Eigenvalues ◽  
Crystal Field Parameters ◽  
Fluorescence And Phosphorescence

The luminescence behaviour of crystalline K3CrF6 is measured in the temperature range from 100 °K to 4.2 °K. The complex shows a very strong, broad fluorescence emission at temperatures lower than 20 °K. additionally also the phosphorescence transition can be observed. At temperatures higher than 20 °K only fluorescence is measured. The 2E→4A2-transition does not split suggesting Oh-site symmetry.Excitation- and luminescence spectra at 4.2 °K are the basis for a calculation of the energy eigenvalues. The crystal field parameters are fitted by the experimental data. The vibrational sidebands of the electronic transitions 2E - 4A2 an 4T24A2 are compared with Raman- and IRresults. From the temperature dependence and measured vibrational frequencies the zero phonon transitions of fluorescence and phosphorescence can be found

Upconversion Luminescence Study of Er3+ in Gadolinium-Calcium- Silicoborate Glasses

2013 ◽  
Vol 770 ◽  
pp. 249-253 ◽  
Author(s):  
Jakrapong Kaewkhao ◽  
Hong Joo Kim ◽  
Smit Insiripong ◽  
Natthakridta Chanthima ◽  
Siriprapa Kaewjaeng ◽  
...  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Upconversion Luminescence ◽  
Optical Devices ◽  
Electronic Transitions ◽  
Potential Candidate ◽  
Melt Quenching ◽  
Absorption Bands ◽  
Green Is ◽  
Glass Series

The new glass series were prepared in compositions 25Gd2O3-10CaO-10SiO2-(55-x) B2O3-xEr2O3 (where x is 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol %) by normal melt-quenching technique at the melting temperature of 1,400 °C. The optical spectra were measured and shown absorption bands were assigned to appropriate f-f electronic transitions of Er3+ ions from the 4I15/2 ground state to the following excited states: 4G11/2, 2H9/2, 4F5/2, 4F7/2, 2H11/2, 4S3/2, 4F9/2, 4I9/2 and 4I11/2. Single peak from upconversion luminescence was observed at 531 nm (green) is assigned to the 2H11/24I15/2. In this work, the strongest peak at 2.0 % mol of Er2O3 was observed. In this work, suggests that the Er3+ ion in gadolinium calcium silicoborate glasses possibly considered as a potential candidate for applications in upconversion-based optical devices.

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