Energy level positions of the nickel 2+/1+ and cobalt 2+/3+ charge states have been used to estimate band edges for the valence and conduction bands of ZnSe-based alloys with cation (ZnCdSe) and anion (ZnSSe) substitution. Chemical trends in band offsets of heterostructures of Zn- or Mn-based II-VI compounds are analysed. Further on, the change of Ni^{2+}(3d^{8}) and Co^{2+}(3d^{7}) intra-d shell transition bands upon the alloying of host material is discussed.
Photoluminescence measurements have been carried out for Zn_{1-x} Cd_{x} Se:Co and ZnS_{x}Se_{1-x}:Co mixed crystals. Changes of recombination channels are observed in mixed crystals as compared to the emission of host binary compounds. Character of changes is slightly different for the alloys with cation and anion substitution. Photoluminescence kinetics of the L-line and of two other Co^{2+} intra-shell emission bands was measured to determine radiative decay rates.
Absorption and reflectivity measurements have been carried out for Zn_{1-x}Cd_{x}Se:Ni and ZnS_{x}Se_{1-x}:Ni solid solutions. Energy level positions of nickel 2+/1+ charge state have been used for estimation of band offsets for the valence and conduction bands of ZnCdSe/ZnSe and ZnSSe/ZnSe. Intra-shell transitions of Ni^{2+} were also studied.
Single crystals of double molybdates and tungstates of the formula KLa_{1-x}Pr_{x}(MO_{4})_{2} (M = Mo, W) with a concentration of Pr^{3+} ions ranging from x=0.1 to x=0.005 have been prepared. Their electronic absorption and emission spectra have been measured and discussed as well as related to their crystal structures. Both the multiphonon relaxation and cross relaxation contribute to the decay of the ^{3}P_{0} level of Pr^{3+} in these two matrices.
The optical excitation and emission spectra of Eu(III) in [Eu_{x}La_{1-x}(AP)_{6}](ClO_{4})_{3} centrosymmetric complex were measured. The vibronic transitions were observed in excitation and emission spectra. Following the vibrational analysis' of the infrared and Raman spectra of [Pr_{x}La_{1-x}(AP)_{6}](ClO_{4})_{3}, the assignment of [Eu_{x}La_{1-x}(AP)_{6}](ClO_{4})_{3} vibronics was given The concentration effect on excitation and emission spectra was investigated. It was found that the vibronic intensities were changed upon the concentration effect. The intensive charge transfer bands were observed in blue region. Their intensities decreased with increasing concentration.
Absorption spectroscopy was used to study the aqueous solution structure of Eu(III) complexes with DTPA (diethylenetriaminepentaacetic acid) and TTHA (triethylenetetraaminehexaacetic acid). Analysis of the oscillator strengths of the 4f ↔ 4f transitions and of the Judd-Ofelt intensity parameters, τ_{λ}, was performed in order to investigate the formation and the type of bonding in Eu(III)-DTPA and Eu(III)-TTHA species occurring in solution. The correlation of these results with those from other methods made it possible to suggest a relatively complete model of Eu(III)-polyaminocarboxylate coordination.
The absorption spectra of [Nd(C_{3}H_{7}NO)(NO_{3})_{3}(H_{2}O)_{3}]·H_{2}O were measured at 293 K and 5 K and the intensities of f-f transitions were investigated. The electron-phonon features observed in absorption spectra were identified and compared with other available data for Nd systems.
The spectroscopic studies of anhydrous neodymium perchlorate in two series of 2-halogeno derivatives of ethyl alcohol are presented. The changes of intensities of ^{4}I_{9/2} → ^{2}G_{7/2}, ^{4}G_{5/2} hypersensitive transitions are discussed within the framework of Mason's polarizability mechanism. Anomalous dependence of band intensities was found for the 2-fluoro derivatives. The linear relation of oscillator strength vs. solvent polarizability was broken for the 2-bromine and 2-iodine derivatives of ethyl alcohol. The effort was made for explanation of such strange results.
Single crystals of lanthanide complexes (Ln = Pr, Nd, Eu) were obtained from aqueous solutions. Optical properties of the title compound are investigated by absorption, excitation, and emission spectra. Probabilities of electronic transitions were analysed and participation of vibronic components in the spectra were found. Temperature effect on the spectra was studied and analysed in terms of cooperative interaction.
Electronic absorption spectra of erbium and dysprosium acetate single crystals were measured. The intensities of 4f-4f transitions were calculated and the Judd-Ofelt Ω_{λ} parameters evaluated. Heavy lanthanide acetates differ from other lanthanide carboxylate compounds by relatively high "hypersensitive" transition intensities and the Ω_{2} parameters. These results are discussed in terms of a stronger polarization effect which can be explained by the distinctly shorter Ln-OH_{2} bond in comparison with the Ln-OOC bond in the investigated system.
Electron absorption and emission spectra of Eu^{3+} ion in stoichiometric KEu(WO_{4})_{2} were measured at the temperature range 15-300 K. The oscillator strengths of f-f transitions and the Judd-Ofelt parameters were evaluated. The assignment of vibronic transitions is given and mechanism of emission decay is discussed.
IR, Raman, electron absorption and emission spectra of KEu(MoO_{4})_{2} crystal were measured at the temperature range 8-300 K. The oscillator strengths of f-f transitions were evaluated.
Absorption and reflectivity measurements were carried out on Zn_{1-x}Mn_{x}Se:Ni solid solutions. The spectra demonstrate the radical change of the structure of internal Ni^{2+}(3d^{8}) transitions at the presence of the Mn ions and strong dependence on Mn concentration. The threshold energy ħω_{th} for the process of Ni photoionization to the valence band Ni^{2+}(3d^{8}) + ħω_{th} → Ni^{1+}(3d^{9}) + h is shifted to the lower energy by 30 meV, but hardly depends on x despite the essential increase in the energy gap.
Two types of lanthanide squarate hydrates of formulae Eu(C_{4}O_{4})(HC_{4}O_{4})(H_{2}O)_{6}·H_{2}O (compound I) and [Ln_{2}(C_{4}O_{4})_{3}(H_{2}O)_{8}] where Ln = Eu and Gd (compound II) were investigated. The optical properties of crystals I and selected spectral data of compound II are reported and confronted with earlier studies of europium complexes type II. Excitation and emission spectra were measured at 77 K. Effect of polymeric structure on spectroscopic properties is considered and correlated with the structural data. Cooperative intrachain interactions between metal ions coupled via squarate anions were pointed and cooperative absorption was recorded. To check the presence of the Eu^{2+} traces, the EPR and γ-irradiation measurements were applied. Raman spectra of the compound II (where Ln = from Sm to Lu) were measured in the range 50-500 cm^{-1}. Positions of the bands were considered in function of ionic radius of lanthanide ion. The above, together with the data from excitation spectra, allows to localize the Ln-O bands. Vibronic components in electronic spectra were elucidated and assigned.
The ^{6}G_{J} → ^{6}P_{J} emission for Gd^{3+} in LiYF_{4} around 600 nm is reported. As far as we are aware, this is the first observation of visible luminescence from trivalent gadolinium.
In the paper the energy states of structured isoelectronic impurities of transition metals and rare earth elements, donor and acceptor excitons of 3d and 4f impurities, the role of donor and acceptor excitons of 3d and 4f impurities in energy transfer from the matrix to impurities are discussed. It is shown that structured impurities may be classified as "open" and "closed" isoelectronic impurities. The number of electrons in the 3d or 4f shells is changed at hω < E_{g} not changed structure levels generated by forbidden gap properties donor acceptor excitons those energy transfer mechanisms from matrix to an impurity (a capture carriers into 3d or 4f shells open and auger process essentially distinguished two kinds structured isoelectronic for closed impurities a model is discussed in frame which the spectra of electroabsorption photoluminescence cathodoluminescence are described.
Single crystals of praseodymium tribromide heptahydrate were grown from aqueous solution. The IR, Raman, and high resolution absorption spectra were measured at room and low temperatures. The assignments of IR and Raman frequencies are reported. The temperature dependence of intensities was found and vibronic coupling in f-f transitions was analysed. Anisotropy of the intensities of optical lines was detected and taken into account in the Judd-Ofelt analysis of the f-f transitions probabilities. The results are compared to the available IR and electron spectroscopic data for other single crystals of lanthanide bromides.
We report a systematic study of the temperature variation of the energy [E_{0}(T)] and broadening parameter [Γ_{0}(T)] of the fundamental band gap of ZnSe in the range 27 K < T < 370 K using contactless electroreflectance. The obtained values of E_{0}(T) and Γ_{0}(T) have been fit to various semi-empirical expressions to obtain information about the exciton-phonon coupling in this system. The experimentally determined E_{0}(T) also is of significance for technological applications since it can be used to determine the operating temperature of ZnSe-based devices such as quantum well lasers.
Two of europium complexes with L- and DL-α-alanine-hydroxamic acids were synthesized. To our knowledge they are the first examples of X-ray and spectral data of lanthanide single crystals with hydroxamic acid derivatives. Both compounds consist of dimers in their structures, formed by two OH bridging groups of amino-hydroxamic acid molecules. Besides, two metal ions are chelated by CO and OH groups, forming five-membered rings. In the complex with L-ligand, different than in the DL-one, two additional perchloric acid molecules are included in crystal cavities and form hydrogen bondings with nitrogen and oxygen atoms of the ligand. Absorption, emission and excitation spectra were measured and analyzed at room and low temperatures. Structural effect of ligand chirality was found and its spectroscopic consequences are reported. The effect of the dimeric structure on spectroscopic properties is discussed.
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