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Ultrafast excited-state dynamics of CuBr3- complex was studied in acetonitrile and dichloromethane solutions using femtosecond transient absorption spectroscopy with 18 fs temporal resolution and quantum-chemical DFT calculations. Upon 640 nm excitation, the CuBr3- complex is promoted to the ligand-to-metal charge transfer (LMCT) state, which then shortly undergoes internal conversion into the vibrationally hot ligand field (LF) excited state with time constants of 30 and 40 fs in acetonitrile and dichloromethane, respectively. The LF state nonradiatively relaxes into the ground state in 2.6 and 7.3 ps in acetonitrile and dichloromethane, respectively. Internal conversion of the LF state is accompanied by vibrational relaxation that occurs on the same time scale. Based on the analysis of coherent oscillations and quantum-chemical calculations, the predominant forms of the CuBr3- complex in acetonitrile and dichloromethane solutions were revealed. In acetonitrile, the CuBr3- complex exists as [CuBr3(CH3CN)2]-, whereas three forms of this complex, [CuBr3CH2Cl2]-, [CuBr3(CH2Cl2)2]-, and [CuBr3(CH2Cl2)3]-, are present in equilibrium in dichloromethane.

Luminescence excitation spectra of BaBrI single crystals doped by divalent lanthanide ions are studied using synchrotron radiation excitations from the MAX IV 1.5 GeV storage ring. The energy of the edge and the formation of core cation exciton as well as the energy threshold of the multiplications of electronic excitations is found. It was clearly established the energy transfer from intrinsic luminescence centers to Sm2+ and Eu2+ ions.

The paper presents the results of a comprehensive study of effects that In3+ ion impurities have on the optical properties of SrF2 and SrF2:Ce3+ crystals. The investigations were carried out both by optical spectroscopy methods and ab initio quantum chemical calculations. To estimate the effect of indium impurities on the optical band gap of the crystals, the DFT calculations were performed for SrF2 crystals doped with different concentrations of In3+ ions. The study of SrF2 crystals co-doped with Ce and In ions reveals the highly effective role of indium ions in reducing the electron trapping efficiency in the processes of excitation transfer to an activator. This improvement is associated with some change in the band gap of the crystals caused by indium doping, which is confirmed by both theoretical and experimental results.

BaBrI crystals activated by Sm2+ ions were synthesized by the Bridgman method. The Sm content in the samples was analyzed by the method of mass spectrometry with inductively coupled plasma. The results of the study of the optical and scintillation characteristics of the synthetic crystals, such as photoluminescence, X-ray luminescence, and absorption spectra, are reported. The light yield of the luminescence of the studied samples was estimated.

Ultrafast excited-state dynamics of CuBr

The absorption spectra of X-ray irradiated alkaline earth fluoride (CaF2, SrF2, BaF2) crystals doped with Sm, Нo, Er, Tm ions are investigated by thermal bleaching of the sample in the 300–700 K temperature range. X-ray irradiation creates absorption bands of inter-configuration 4fn-4fn−1-5 d1 transitions of divalent impurity ions and F3− and (F2−)ii hole centers. The thermal oxidation of the divalent RE ions have been observed. Two possible mechanism of thermal oxidation of divalent lanthanide ions in alkaline-earth fluorides are discussed.

The features of using the Bridgman method for growing alkaline earth halides crystals BaBrI, BaClI, and SrBrI are discussed. The results of the study of scintillation characteristics of grown crystals activated by europium ions are presented. The actual content of europium in crystals is determined and the values of the luminescence yield and decay time are estimated. X-ray luminescence and absorption spectra of the obtained crystals are given.

The results of nonempirical quantum chemical calculations of CaF2, SrF2, and BaF2 crystals that were activated by In3+ and Ga3+ ions have been presented. The calculations were performed in the framework of density functional theory using the VASP software complex. The estimation of the width of the band gap of defect-free crystals have been carried out by different methods and the influence of impurity ions on the band gap width has been estimated as well as the possibility of getting rid of shallow traps by introducing an impurity of indium or gallium has been investigated.

Ultrafast excited-state dynamics of CuCl42– in acetonitrile is studied by femtosecond broadband transient absorption spectroscopy following excitation of the complex into all ligand-field (LF or d–d) states and into the two ligand-to-metal charge transfer (LMCT) states corresponding to the most intense steady-state absorption bands. The LF excited states are found to be nonreactive. The lowest-lying 2E LF excited state has a lifetime less than 150 fs, and the lifetimes of the second (2B1) and the third (2A1) LF excited states are 1 and 5 ps, respectively. All three LF states decay directly into the ground 2B2 state. Such significant differences in excited-state decay time constants were rationalized computationally through time-dependent density functional theory (TD-DFT) computations. TD-DFT mapping of the relaxation pathway along the symmetric Cl–Cu–Cl umbrella bending vibration gives evidence for a conical intersection between the 2E excited state and the ground 2B2 state. The LMCT states decay within ...

The results of spectrophotometric study and quantum chemical calculations for copper(II) chloro- and bromocomplexes in acetonitrile are reported. Electronic spectra of the individual copper(II) halide complexes were obtained in a wide spectral range 200–2200 nm. Stability constants of the individual copper(II) halide complexes in acetonitrile were calculated: log β1 = 8.5, log β2 = 15.6, log β3 = 22.5, log β4 = 25.7 for [CuCln]2−n and log β1 = 17.0, log β2 = 24.6, log β3 = 28.1, log β4 = 30.4 for [CuBrn]2−n. Structures of the studied complexes were optimized and electronic spectra were simulated using DFT and TD-DFT methodologies, respectively. According to the calculations, the more is the number of halide ligands the less is coordination number of copper ion.

Using the example of Russian and European clinical guidelines on diagnosis and treatment of heart failure the article addressed issues, which may arise from word-for-word or component-wise translation to Russian of some English medical terms, such as bendopnea (or flexodyspnea, a symptom of shortness of breath when bending forward), a symptom (subjective symptom), and a sign (objective symptom).

The work is necessitated by search for new materials to detect ionizing radiation. The rare-earth doped ternary alkali earth-halide systems are promising scintillators showing high efficiency and energy resolution. Some aspects of crystal growth and data on the structural and luminescence properties of BaBrI and BaClI doped with low concentrations of Eu 2 + ions are reported. The crystals are grown by the vertical Bridgman method in sealed quartz ampoule. New crystallographic data for BaClI single crystal obtained by single crystal X-ray diffraction are presented. Emission, excitation and optical absorption spectra as well as luminescence decay kinetics are studied under excitation by X-ray, vacuum ultraviolet and ultraviolet radiation. The energies of first 4f-5d transition in Eu 2 + and band gaps of the crystals are obtained. The electronic band structure of the crystals are calculated using density functional theory as implemented in Vienna Ab initio Simulation Package. Calculated band gap energies are in accordance with the experimental estimates. The energy gaps between the valence band maximum and occupied Eu 2 + 4f levels in BaBrI and BaClI are suggested. In addition, vacuum referred binding energy diagram of lanthanide levels is constructed using the chemical shift model.

The results from ab initio quantum chemical calculations for inorganic scintillators BaBrI:Eu2+ and BaСlI:Eu2+ are presented. The calculations were performed using the density functional theory and the VASP software package. Estimates are made for the band-gap width of the crystals, and for the locations of 4f- and 5d-levels of Eu2+ ions with respect to the valence and conduction bands, respectively, and the possibility of using a new material based on BaСlI:Eu2+ as a scintillator is evaluated.

Nonradiative relaxation dynamics of CuCl42– complexes photoexcited into the highest-energy ligand-field electronic state (2A1) is studied in acetonitrile, dichloromethane, and chloroform solvents, as well as in acetonitrile–water and in acetonitrile–deuterated water mixtures. Due to ultrafast internal conversion, this excited state directly converts to the electronic ground state in dichloromethane and chloroform. The nonradiative relaxation constant is similar in anhydrous acetonitrile. Addition of water to acetonitrile solutions efficiently quenches the excited ligand-field 2A1 state. The quenching is proposed to be due to the diffusion-controlled formation of an electronically excited pentacoordinated [CuCl4H2O]2– encounter complex or a short-lived exciplex of similar structure, in which the electronic excitation energy transfers into the O–H stretch of the coordinated H2O molecule. This is followed by the dissociation of the pentacoordinated species, resulting in the reformation of the ground-state Cu...

BaBrI crystals containing 0.01 to 8 mol. % of Eu2+ activator have been obtained. The photo- and X-ray luminescence spectra correspond to Eu2+ 5d – 4f characteristic transitions with a maximum at about 3 eV. The scintillation decay time is 400-500 ns (fast component) and 3700–5500 ns (slow component). It has been established that the decay time in BaBrI crystals depends on the activator concentration. In the absorption spectra of BaBrI: Eu2+ crystals, a double peak is observed associated with 4f7 – 4f65d1 transitions in Eu2+. On the edge of optical absorption, the band gap of 5.2 eV was estimated. We assume the resonant mechanism of energy transfer to the luminescence centers.

We report data on the luminescence spectra associated with photochromic centers in X-ray irradiated calcium fluoride crystals doped with Lu ions. Irradiation in low energy photochromic centers absorption band excites emission, which can be identify with transitions into photochromic centers. Ab initio calculation of absorption spectrum of photochromic center agrees rather well with experimental data.

Using the example of Russian and European clinical guidelines on diagnosis and treatment of heart failure the article addressed issues, which may arise from word-for-word or component-wise translation to Russian of some English medical terms, such as bendopnea (or flexodyspnea, a symptom of shortness of breath when bending forward), a symptom (subjective symptom), and a sign (objective symptom).

In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy transfer processes from host to Eu$^{2+}$ ions are established., Comment: 5 pages, 4 figures, LUMDETR 2018 conference poster presentation, submitted to Radiation measurements

This letter reports the results of ab initio calculations of absorption spectra of Cu + ion embedded in LiF and NaF matrices. The calculations have been performed in embedded cluster approach at hybrid density functional theory (DFT) level. We propose the model of oscillator strength and absorption intensity calculations for forbidden 3d 10 → 3d 9 4s transitions based on the linear dependence between transitions dipole matrix elements and copper ion displacements. For LiF:Cu + crystal one should expect two bands in absorption spectra at 5.32 and 5.88 eV with different intensity ratios: the low energy band is more intense than the high energy band.

Nonradiative relaxation dynamics of CuCl

We have studied the absorption spectra of radiation-induced divalent cerium and praseodymium ions in crystals of alkaline-earth fluorides. Using ab initio quantum-mechanical methods, we have calculated absorption spectra of divalent praseodymium ions in CaF2 crystals for the first time. The theoretical spectrum agrees rather well with the experimentally registered spectra.

Using ab initio methods and taking into account the lattice relaxation and polarization caused by the occurrence of the core hole, we have studied theoretically the cross luminescence in barium fluoride crystals in terms of the embedded-cluster approach. Two schemes of modeling of the core hole have been performed—in the form of an additional point charge and in the form of the 5p state of the barium ion. Calculations have been done both by the Hartree-Fock method and by the density functional method. We have showed that the deformation of the lattice caused by the occurrence of the core hole leads to states localized on fluorine ions of the nearest environment splitting off from the valence band of the BaF2 crystal. The cross-luminescence bands at 5.7, 6.3, and 7.1 eV are caused by transitions from these localized states. We have also showed that the low-energy edge of the cross luminescence is formed by transitions from states that are localized on ions of the second coordination sphere.

Photochemistry of copper(II) monochlorocomplexes in methanol and acetonitrile solutions is studied by UV-pump/broadband deep-UV-to-near-IR probe femtosecond transient absorption spectroscopy. Upon 255 and 266 nm excitation, the complexes in acetonitrile and methanol, respectively, are promoted to the excited ligand-to-metal charge transfer (LMCT) state, which has a short (sub-250 fs) lifetime. From the LMCT state, the complexes decay via internal conversion to lower-lying ligand field (LF) d-d excited states or the vibrationally hot ground electronic state. A minor fraction of the excited complexes relaxes to the LF electronic excited states, which are relatively long-lived with lifetimes1 ns. Also, in methanol solutions, about 3% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming copper(I) solvatocomplexes and chlorine atoms, which then further react forming long-lived photoproducts. In acetonitrile, about 50% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming radical and ionic products in a ratio of 3:2. Another minor process observed following excitation only in methanol solutions is the re-equilibration between several forms of the copper(II) ground-state complexes present in solutions. This re-equilibration occurs on a time scale from sub-nanoseconds to nanoseconds.

In this paper we present the results of an ab initio calculations of df-absorption spectra for alkaline earth fluoride matrix doped with Pr3+ and Ce3+ ions. The density-functional theory (DFT) calculations have been performed in embedded-cluster approach. All our results were obtained with taking into account the lattice relaxation in the presence of trivalent impurity ion. The calculation have been made both for cubic and tetragonal centers. For the tetragonal centers we estimate the crystal field splitting of eg level.

LiF single crystals with copper impurity (0.0004–0.002%) have been grown by the Czochralski method and investigated. The luminescence, excitation, and optical absorption spectra have been recorded. The luminescence spectrum contains a band at 450 nm upon 250-nm excitation. This band is attributed to Cu+ centers in the samples grown. The mechanisms of capture and recombination during thermoluminescence are considered.

A spatial and temporal diversity of processes and phenomena is observed in mountaintaiga landscapes as the object of management. A knowledge of the mechanisms of their interactions makes it possible to effectively manage these processes and phenomena. The methodology of system analysis and mathematical models of interaction mechanisms are used in the analysis of these phenomena. A visualization of modelling results is carried out using geoinformation mapping methods.

This paper reports on a study of cross-luminescence in barium fluoride crystals doped by a variety of impurities (K+, Cd2+, Y3+, Yb3+, La3+). It is shown that doping of the crystal with a trivalent impurity gives rise to the formation of an additional cross-luminescence band peaking at 7.5 eV, the intensity of this band increasing with increasing impurity concentration.

This paper presents both investigations of high-energy luminescence with maximum at 7.5 eV in BaF2:Y3+ and BaF2:Yb3+ crystals and theoretical calculations of cross-luminescence spectrum in crystals of barium fluoride with interstitial ions of fluorine. The dependencies of the 7.5 eV emission intensity as function of different impurities mol. concentration are presented. The intensity of this emission increases with concentration of rare-earth impurity, but in the case of doping by Yb3+ and Y3+ this intensity is less than that in the case of La3+ doping. This feature (as well as the nonlinear dependence) can be due to the creation of clusters, i.e., aggregation of impurity ions and F--interstitials. The intensity of the 7.5 eV luminescence in a BaF2:Y3+ crystal after annealing at 1000 K increased by three times but it remained less than in the case of La3+ doping. Theoretical calculations of the core hole electronic and spatial structure and cross-luminescence spectrum were performed in the [Ba6F12] cluster. This cluster contains interstitial ion of fluorine, which is surrounded by six ions of Ba2+. In the case of using Hartree-Fock method the calculated luminescence spectrum of BaF2 crystal with interstitial fluorine shows cross-luminescence band with main maximum at 5.2 eV and high-energy band at 11.7 eV. In the case of using TD DFT method the energies of both cross-luminescence transitions and of transition between interstitial ion and core levels are in satisfactory agreement with experimental data, being all overestimated by approximately the average value of 0.8 eV.

We have studied the absorption spectra of x-ray irradiation-induced Ce2+ and Pr2+ ions in crystals of alkaline-earth fluorides. We have calculated absorption spectra of divalent praseodymium ions in SrF2 crystals doped with Pr2+ for the first time. The calculated spectra agree rather well with the experimental data. In crystals containing induced Ce2+ ions we have found strong electron-phonon coupling. In BaF2, we do not observe bands corresponded to divalent Ce or Pr ions., Comment: 14 pages, 5 figures, 1 table

In this paper we present the results of ab initio calculations of charge-transfer absorption bands in Eu3+ and Yb3+-doped CaF2 and SrF2 crystals, which are due to transitions from the top of valence band to 4f state of trivalent rare-earth ion. The density-functional theory calculations have been performed in embedded-cluster approach. It was shown that low-energy absorption band is caused by charge-transfer transitions between 2p-states of interstitial fluorine and 4f state of the impurity ion.

The single crystals LiF with copper impurity were grown by Czochralski method. The concentrations of Cu in the crystals were 0,0004-0,002%. In order to determine a copper valence impurity, measurements of the ESR, emission, excitation and absorption spectra were performed. We found emission peak at 410 nm and excitation peak at 250 nm. In agreement with reference, these peaks point to presence of Cu+ in our samples. The mechanisms of capture and recombination providing process of thermoluminescence were recognized.