excitation spectra
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2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Aleksandar Ćirić ◽  
Łukasz Marciniak ◽  
Miroslav D. Dramićanin

AbstractJudd–Ofelt theory is a cornerstone of lanthanides’ spectroscopy given that it describes 4fn emissions and absorptions of lanthanide ions using only three intensity parameters. A self-referenced technique for computing Judd–Ofelt intensity parameters from the excitation spectra of Eu3+-activated luminescent materials is presented in this study along with an explanation of the parametrisation procedure and free user-friendly web application. It uses the integrated intensities of the 7F0 → 5D2, 7F0 → 5D4, and 7F0 → 5L6 transitions in the excitation spectrum for estimation and the integrated intensity of the 7F0 → 5D1 magnetic dipole transition for calibration. This approach facilitates an effortless derivation of the Ω6 intensity parameter, which is challenging to compute precisely by Krupke’s parametrisation of the emission spectrum and, therefore, often omitted in published research papers. Compared to the parametrisation of absorption spectra, the described method is more accurate, can be applied to any material form, and requires a single excitation spectrum.


2022 ◽  
Author(s):  
Kaiyuan Cao ◽  
Ming Zhong ◽  
Peiqing Tong

Abstract We study the dynamical quantum phase transitions (DQPTs) in the XY chains with the Dzyaloshinskii-Moriya interaction and the XZY-YZX type of three-site interaction after a sudden quench. Both the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form $H=\sum_{k}\varepsilon_{k}(\eta^†_{k}\eta_{k}-\frac{1}{2})$, where the quasiparticle excitation spectra $\varepsilon_{k}$ may be smaller than 0 for some $k$ and are asymmetrical ($\varepsilon_{k}\neq\varepsilon_{-k}$). It's found that the factors of Loschmidt echo equal 1 for some $k$ corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfying $\varepsilon_{k}\cdot\varepsilon_{-k}<0$, when the quench is from the gapless phase. By considering the quench from different ground states, we obtain the conditions for the occurrence of DQPTs for the general XY chains with gapless phase, and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Besides, we also analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. The conclusion can also be extended to the general quantum spin chains.


2022 ◽  
Author(s):  
Fabian Bauch ◽  
Chuanding Dong ◽  
Stefan Schumacher

Lewis acid doping of organic semiconductors (OSCs) opens up new ways of p-type doping and has recently become of significant interest. As for the mechanistic understanding, it was recently proposed that upon protonation of the OSC backbone, electron transfer occurs between the protonated polymer chain and a neutral chain nearby, inducing a positive charge carrier in the latter [Nat. Mater. 18, 1327 (2019)]. To further clarify the underlying microscopic processes on a molecular level, in the present work, we analyze the influence of protons on the electronic properties of the widely used PCPDT–BT copolymer. We find that single protonation of the polymer chain leads to the formation of a polaron coupled to the position of the proton. Upon protonation of the same chain with a second proton, an intrachain electron transfer occurs, leaving behind a polaron largely decoupled from the proton positions. We also observe the possibility of an interchain electron transfer from a neutral chain to a double protonated chain in agreement with the mechanism recently proposed in the literature. The simulated vertical excitation spectra for an ensemble of protonated species with different amounts of protons enable a detailed interpretation of experimental observation on PCPDT–BT doped with the Lewis acid BCF. Our results further suggest that multi-protonation plays an important role for completing the mechanistic picture of Lewis acid doping of OSCs.


2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Emre Ergeçen ◽  
Batyr Ilyas ◽  
Dan Mao ◽  
Hoi Chun Po ◽  
Mehmet Burak Yilmaz ◽  
...  

AbstractIn van der Waals (vdW) materials, strong coupling between different degrees of freedom can hybridize elementary excitations into bound states with mixed character1–3. Correctly identifying the nature and composition of these bound states is key to understanding their ground state properties and excitation spectra4,5. Here, we use ultrafast spectroscopy to reveal bound states of d-orbitals and phonons in 2D vdW antiferromagnet NiPS3. These bound states manifest themselves through equally spaced phonon replicas in frequency domain. These states are optically dark above the Néel temperature and become accessible with magnetic order. By launching this phonon and spectrally tracking its amplitude, we establish the electronic origin of bound states as localized d–d excitations. Our data directly yield electron-phonon coupling strength which exceeds the highest known value in 2D systems6. These results demonstrate NiPS3 as a platform to study strong interactions between spins, orbitals and lattice, and open pathways to coherent control of 2D magnets.


2022 ◽  
Vol 130 (1) ◽  
pp. 121
Author(s):  
В.И. Царюк ◽  
К.П. Журавлев

The luminescence excitation energy transfer in europium and terbium indole-3-carboxylates, indole-3-acetates and indole-3-propionates as well as ternary indolecarboxylates containing 1,10-phenanthroline and 2,2'-bipyridine molecules have been studied. The luminescence excitation spectra, the lifetimes of the 5D0 (Eu3+) and 5D4 (Tb3+) states, and the luminescence intensity are analyzed. The decisive role of ligand-metal charge transfer (LMCT) states in the quenching of the luminescence of europium aromatic carboxylates containing a π-excessive pyrrole or indole fragment is demonstrated. Most europium compounds are characterized by quenching due to the depopulation of the 5D0 state of the Eu3+ ion through the low-energy LMCT state. But in some ternary compounds, the LMCT state being of higher energy participates in the nonradiative depopulation of the excited electronic states of the ligand.


Author(s):  
Ali Ghafarloo ◽  
Reza Sabzi ◽  
Naser Samadi ◽  
Hamed Hamishehkar

Synthesis of carbon dots (CDs) from natural resources not only enables green synthesis and production of environmentally friendly materials, but also provides a cost-effective probe as a fluorescence nanosensor. The proposed sensor introduces a unique one-pot hydrothermal CDs synthesis from alfalfa leaves, which is promising for sensing hydrochlorothiazide (HCTZ) via inner filter effect (IFE) and resonance Rayleigh scattering (RRS). The as-prepared CDs had wide emission spectra, excitation-dependent emission, high solubility, high stability, and visible fluorescence light with a quantum yield of up to 11%. The absorption of HCTZ overlapped with the excitation spectra of CDs. Therefore, CDs represented excellent quenching due to IFE when HCTZ was gradually added. Furthermore, this fluorescent sensor was successfully used to quantify HCTZ in the linear ranges (0.17-2.50 μg mL-1) with the limit of detection of 0.11 μg mL-1. The sensing system was simple as no surface functionalization was required for CDs, leading to less laborious steps and more cost-effective synthesis. The reaction time was short, i.e., less than 2 min, indicating a simple approach for rapid analysis of HCTZ. By optimizing conditions, successful measurements were carried out on pharmaceutical tablets.


Author(s):  
В.П. Смагин ◽  
А.А. Исаева ◽  
Е.А. Шелепова

Nanoscale particles ZnS:Nd3+, CdS:Nd3+ and (Zn,Cd)S:Nd3+ were synthesized and doped in a polymerizing methyl methacrylate medium during the production of optically transparent polyacrylate composites of the composition PMMA/ZnS:Nd3+, PMMA/CdS:Nd3+ and PMMA/(Zn,Cd)S:Nd3+. The excitation of photoluminescence (FL) and FL of semiconductor structures in composites is associated with the transition of electrons from the valence band to the conduction band and to the levels of structural defects of semiconductor particles, followed by recombination at these levels. Based on changes in the excitation spectra of FL and FL composites, assumptions are made about the structure of particles, the distribution of Nd3+ ions in it and their effect on photoluminescence.


2022 ◽  
Vol 64 (1) ◽  
pp. 105
Author(s):  
С.З. Шмурак ◽  
В.В. Кедров ◽  
А.П. Киселев ◽  
Т.Н. Фурсова ◽  
И.И. Зверькова

The structure, IR, luminescence, and luminescence excitation spectra of Ce3+, Tb3+, and Eu3+ ions in Lu1−2xCexEuхBO3 and Lu0.91−2xCexTb0.09EuхBO3 solid solutions were studied. The minimum "threshold" distance between Ce3+ and Eu3+ ions was estimated, at which there is no charge transfer between these ions, leading to the quenching of Ce3+ and Eu3+ luminescence. It is shown that in Lu0.91−2xCexTb0.09EuхBO3 compounds, the range of Ce and Eu concentrations of 0.2 – 0.25 at. % is optimal for obtaining the maximum luminous intensity of this compound.


2022 ◽  
Vol 130 (2) ◽  
pp. 300
Author(s):  
А.С. Шишов ◽  
А.Г. Мирочник

The interaction of tris-dibenzoylmethanate Eu(III) with dimethylamine and ammonia vapors was investigated. It was found that when vapors of aqueous solutions of analytes are exposed to tris-dibenzoylmethanate Eu(III) impregnated into the SiO2 matrix, an optical response is observed in the form of an increase in the luminescence intensity of Eu(III). Changes in the luminescence spectra and luminescence excitation of this sensor are analyzed, both under the quenching action of water vapor and under the sensitizing action of analyte vapors. The main points recorded in the excitation spectra are noted, which are important for understanding the processes occurring in the near environment of the lanthanide center. The luminescent chemosensor is promising for creating sensors for detecting ammonia and amines in food safety control and environmental monitoring. Shishov A.S., Mirochnik A.G.


Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 77
Author(s):  
Nicole Nowak ◽  
Rafal Jakub Wiglusz

In this study, nanosized vanadate-substituted hydroxyapatites doped with 1 mol% and 2 mol% Eu3+ ions were obtained via the precipitation method. To evaluate the structure and morphology of the obtained compounds, the XRPD (X-ray powder diffraction) technique, Rietveld refinement, SEM-EDS (scanning electron microscopy-energy-dispersive spectrometry) and TEM (transmission electron microscopy) techniques as well as FTIR (Fourier transform infrared) spectroscopy were performed. Moreover, the chemical formula was confirmed using the ICP-OES (Inductively coupled plasma optical emission spectroscopy spectroscopy). The calculated average grain size for powders was in the range of 25 to 90 nm. The luminescence properties of vanadium-substituted hydroxyapatite were evaluated by recording emission spectra and excitation spectra as well as luminescence kinetics. The crucial step of this research was the evaluation of the biocompatibility of the synthesized nanomaterials. Therefore, the obtained compounds were tested toward sheep red blood cells and normal human dermal fibroblast to confirm the nontoxicity and biocompatibility of new nanosized Eu3+ ion-doped vanadate-hydroxyapatite. Moreover, the final step of the research allowed us to determine the time dependent ion release to the simulated body fluid environment. The study confirmed cytocompatibility of vanadium hydroxyapatite doped with Eu3+ ions.


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