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Samarium-doped calcium fluoride (CaF2) nanoparticles were synthesized by the co-precipitation method and characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), optical absorption and photoluminescence (PL) techniques. The PXRD patterns confirmed the cubic crystallinity of the synthesized nanoparticles. The average particle size estimated using Scherer's formula was ∼20 nm. The purity of the synthesized nanoparticles was confirmed by the FTIR spectrum. The morphological features studied using SEM revealed that the nanoparticles were agglomerated and porous. The optical absorption spectrum showed a strong and prominent absorption peak at ∼264 nm and a weak one at ∼212 nm. The PL spectrum showed broad and prominent emissions with peaks at ∼387 and 532 nm along with weak emissions at 573 and 605 nm. [ABSTRACT FROM AUTHOR]

Based on azo group and anthraquinone moiety, new black matrix pigment materials AAQ and DAAQ were synthesized for the first time through Suzuki C-N coupling. As a result of verifying UV-visible absorption spectra of the synthesized materials, DAAQ was found to absorb the entire visible region in 400 ∼ 800 nm in solution state with high extinction coefficient of 8.1 × 103 L/cm · mol. Realization of black color using a single material is expected to be useful for black matrix application. Also in film state made through spin coating, both AAQ and DAAQ absorbed the entire visible region. [ABSTRACT FROM AUTHOR]

We have shown that an ultranarrow dark region can be associated with the feature of significant amount of vaccuum-Rabi splitting in the absorption spectrum of a weak coherent field probing a two-level atom strongly coupled to two degenerate cavity-modes with preselected polarizations. The cavity-induced transparency is produced by the decay-interference of the two independent cavity modes interacting with the same reservoir. It has been shown that the resonant probe transparency is independent of the individual decay rates of the cavity modes. The present model exhibits the possibility of obtaining the narrow dark transparency associated with the significant amount of Rabi splitting in the absorption spectrum with the appreciable value of the cavity-losses. [ABSTRACT FROM AUTHOR]

Mottramite mineral from Tsumeb Corporation Mine, Tsumeb, Otavi, Namibia, is investigated in this present work. The mineral contains vanadium and copper contents of 22.73% and 16.84% by weight, respectively, as V2O5 and CuO. An electron paramagnetic resonance (EPR) study confirmed the presence of Cu(II) with g = 2.2. The optical absorption spectrum of mottramite indicates that Cu(II) is present in a rhombic environment. Near infrared results are due to water fundamentals. [ABSTRACT FROM AUTHOR]

ZnS and Co2+: ZnS nanocrystals were prepared in aqueous solution by one-pot method using thioglycolic acid as stabilizer. The nanocrystals were characterized by X-ray diffraction (XRD), FT-IR spectra and UV-Vis absorption spectra. The results show that both ZnS and Co2+: ZnS nanocrystals possess zinc-blende strcture. The host nanocrystals size dependence of Co2+ doping was investigated experimentally. Well match in ionic radii of Co (0.74 Å) and Zn (0.74 Å) should be responsible for the easier substitutionally doping growth than that of other Co2+ doped chalcogenide nanocrystals. [ABSTRACT FROM AUTHOR]

Effects of point charges on the excitation energies of protonated Schiff base of retinal (PSBR) in gas phase have been investigated by means of time-dependent density functional theory (TD-DFT) method in order to shed light on the electrostatic effects on the absorption spectra of PSBR. The positive and negative charges around PSBR were tested for 11-cis of PSBR. The TD-DFT calculations indicated that the first and second excitation energies are blue-shifted by the existence of the negative charge around the N-H site of PSBR, whereas those are red-shifted by positive charge. On the other hand, the spectral feature in β -ionone ring was much different from that of the N-H site: the first and second excitation energies are red-shifted by the negative charge. The spectral feature is drastically changed at the polyene part of PSBR. It was found that the excitation energies of PSBR are affected strongly by the electrostatic environment. The effects of electrostatic interaction on the absorption spectra of PSBR are discussed on the basis of theoretical results. [ABSTRACT FROM AUTHOR]

The molecular structures, electronic structures and absorption characters of-CH3,-C2H5,-CF3,-C2F5 substituted 5-(2-pyridyl) pyrazolate boron complexes were presented by density functional theory (DFT). The ground state structures of the title complexes were optimised at B3LYP/6-31G* level. In addition, a time dependent density functional theory (TD-DFT) method is applied to investigate the properties of absorption spectra and electronic transition mechanism which were based on the ground state geometries. The results show that the chemical bond formed between nitrogen in the pyridyl ring and boron can be attributed to coordination effect. The boron centre has a typical tetrahedral geometry with the adjacent atoms. The calculated absorption wavelengths for-CF3,-C2F5 substituted 5-(2-pyridyl) pyrazolate boron complexes are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

We propose an exactly solvable model for the two-state curve-crossing problem. Our model assumes the coupling to be a delta function. It is used to calculate the effect of curve crossing on the electronic absorption spectrum and the resonance Raman excitation profile. [ABSTRACT FROM AUTHOR]

Two types of melanin films: self-arranged ordered films and amorphous films have been studied in the present paper. The structure, absorption spectra, spectra of photovoltage, and spectra of time-resolved photoluminescence have been investigated for both types of melanin films. Time-resolved photoluminescence was measured at room temperature at different delay times. The reason for the difference in the electronic properties of structurized and amorphous films of melanin is attributed to the structural features of the films related to ordered dendrite-like structures and amorphous disordered ones, respectively. [ABSTRACT FROM AUTHOR]

The reaction of aroyl isothiocyanates with 1-aminoanthraquinone or 2-aminoanthraquinone in ionic liquids leads to an efficient synthesis of N-substituted N' -aroylthioureas, containing 9,10-anthraquinone moiety, in 70-95% yields. All of the pigments were fully characterized by 1H NMR, 13C NMR, IR, and UV-vis absorption spectra. [ABSTRACT FROM AUTHOR]

The study reported herein is focused on measuring, as well as on modeling numerically, the positions and intensities of the absorption bands in the electronic spectrum of benzene ring-based mono-azo dyes, while preserving their potential mesogenic ability. Both non-polar structures, as well as highly polar push-pull structures, of azo dye molecules were designed and studied. [ABSTRACT FROM AUTHOR]

Forty cold bands and 29 hot bands are reported from the high resolution Fourier transform (FT) absorption spectrum of 13CH12CH, all leading to vibrational states located between 6750 and 9500 cm-1. Each of these bands has been vibrationally assigned and rotationally analysed. The band centres (νc), vibrational term values (Gv) and rotational constants are listed. [ABSTRACT FROM AUTHOR]

Semiconductor nanoparticles have attracted much interest during the past decade due to their unique size-dependent chemical and physical properties. These properties emerge from the high surface-to-volume ratio present in nanoparticles. CdS nanoparticles have potential applications as optoelectronic devices, lasers, photocatalysts, electrochemical cells, fluorescent labelling of cell organelles. A series of cadmium sulphide (CdS) nanocrystalline were synthesized by precipitation from a mixture of aqueous solutions of various cadmium salts and sodium thiosulphate at room temperature without adding any surface-termination agent. Their crystal structure and particle size were determined by X-ray diffraction. The fluorescence of CdS nanocrystalline and UV-Vis absorption spectra were also recorded. The relationship between the synthesis conditions and spectroscopic properties was studied. Several factors affect the absorbance and fluorescence spectra, including the cadmium source and Cd:S molar ratio. It has found that in all cases the powders have good morphology when scanned through the SEM. [ABSTRACT FROM AUTHOR]

A significant spectral change from solution to vacuum-deposited films was observed in a 2,3-dicyanopyrazine dye, 5-t-butyl-6-[4-(dibutylamino)styryl]-2,3- dicyanopyrazine. In absorption spectra, a large hypsochromic shift was recognized. On the other hand, a large bathochromic shift occurred in fluorescence with considerable fluorescence quenching. The dye films were characterized as the single crystal phase, then estimation of exciton interaction was carried out on the basis of the crystal data. The result indicated that the electronic states of the dye films are considered to be similar to those of H-aggregates. [ABSTRACT FROM AUTHOR]

Novel polyazomethines containing triphenylamine structure in the main chain have been prepared on a way of polycondensation of 4,4'-diformyltriphenylamine with aromatic diamines in HMPT solution with the goal to study interactions between polymer chain (Ps) and dopant (methanesulfonic acid: MSA, m-cresol: MC and p-chlorophenol: pClp) by FTIR, UV-vis and PL measurements. The electronic absorption spectra and photoluminescence spectra of polyazomethines detected in various solutions were dependent on the diamines structures and could be tuned by supramolecular modification via protonation or H-bond formation of imine group with the dopant. Preliminary results suggest that the polyazomethines can be blue light emitting materials. [ABSTRACT FROM AUTHOR]

Nanoparticles of 1-phenyl-3-naphthyl-5-((ethoxy)phenyl)-2-pyrazoline with sizes ranging from tens to hundreds of nanometers were prepared by the reprecipitation method. Their excitonic transitions responsible for absorption and emission, as compared with those of diluted solution, have been investigated as a function of nanoparticle size. We found that pyrazoline nanoparticles possess an ambiguous size dependence on their optical properties. As the nanoparticle size decreased, the absorption peak of pyrazoline nanoparticles was observed to be shifted to the high-energy side due to size effect. [ABSTRACT FROM AUTHOR]

We have computed the absorption spectra of a large series of anthraquinone dyes using four semi-empirical and ab initio approaches. Without fitting, the ZINDO//AM1 and CIS//HF schemes provide only poor estimates of the λmax of substituted anthraquinones, with mean absolute errors (MAE) of 80 and 180 nm, respectively, for a set of 45 dyes. These approaches are therefore unable to deliver correct estimates of the colour of anthraquinones. On the contrary, TD-DFT schemes appear to be much more robust and provide MAE under the 20 nm limit. If one uses experimental input to calibrate the theoretical values, subsequently allowing a statistical treatment, the theory-experiment discrepancies become comparable (MAE between 11 and 13 nm) for all four approaches. [ABSTRACT FROM AUTHOR]

Infrared absorption spectra of N,N′-dimethyl formamide in the absence and presence of water, rhodamine 6G and water–rhodamine 6G mixture are reported. Assignment of observed bands has been made on the basis of density functional theory calculations and available assignments in the literature. Certain bands show changes in their positions and intensities when water is added to N,N′-dimethylformamide. This is due to hydrogen bonding interaction between these molecules. Similar changes are also observed for dimethylformamide and Rh6G mixture to a lesser extent. The presence of Rh6G in a dimethylformamide–water mixture reverses these spectral changes due to preferential solvation of Cl- by water molecules. Solvation reduces or nullifies the hydrogen bonding between dimethylformamide and water in the mixture. [ABSTRACT FROM AUTHOR]

The weak probe field spectrum of a three-level atom, in the ladder configuration, is obtained. The lower transition of atom is coupled with squeezed vacuum, while the upper transition is coupled to coherent cavity mode and a bath. In this paper, the effect of the various quantities (detuning, decay rates) on the absorption spectrum is investigated. [ABSTRACT FROM AUTHOR]

Absorption spectra and spectra of time-resolved and stationary photoluminescence (PL) measured at low and room temperatures have been investigated for the water- soluble and water-insoluble forms of a melanin pigment, as well as melanin extracted from human hairs whose color is defined by the melanin content. The results obtained can be explained by a complexity of the melanin structure which has, probably, conjugated linear parts and clustered parts with different physical p rope flies. [ABSTRACT FROM AUTHOR]

A series of monogadolinium metallofullerenes of Gd@C80, Gd@C82 (II), and Gd@C82 (HI) was produced and isolated by an efficient multi-stage HPLC method for the first time. All these newly isolated metallofullerenes were characterized by LD-TOF mass spectrometry and Vis-NIR absorptitm spectroscopy. Their possible molecular symmetries are discussed according to their HPLC retention times and absorption spectra. [ABSTRACT FROM AUTHOR]

A mixed quantum classical molecular dynamics (QCMD) simulation of the silver and sodium cations in presence of an excess electron is reported. The silver cation is shown to be reduced by the hydrated electron and to form a stable, highly polarized, neutral atom. On the contrary, the sodium cation is not reduced and a metastable contact ion pair is observed. The resulting absorption spectra of both species are compared with experiments and shown to be in good agreement. Furthermore, the free energy curve for the charge separation was calculated and rationalized in terms of a thermodynamic cycle. Finally, a direct, reactive, molecular dynamics trajectory provides some useful informations on the reduction mechanism. [ABSTRACT FROM AUTHOR]

The covalency of the chemical bonding in perovskites is shown to lead to correlations of ionic displacements, which can result in the appearance of additional lines in X-ray absorption spectra. These possibilities are discussed in connection with the explanation of the nature of the ferroelectric phase transition in prototype ferroelectrics like BaTiO 3 and KNbO 3 . [ABSTRACT FROM AUTHOR]

The synthesis and the spectroscopic properties of a bichromophoric ruthenium trisbipyridyl-1,4-diethynylenebenzene-pyrene system (Ru-b-Py) and the corresponding pyrene ligand (b-Py) are reported. The ruthenium model systems Ru-b-OH, Ru-b-Ph are also presented. UV-Vis absorption and emission at room and low temperature and time-resolved spectroscopy are discussed. For the Ru-b-Py dyad, a mixing of the 3 MLCT state of the ruthenium-based component and the triplet state of pyrene, 3 Py, is observed. Time-resolved transient absorption studies performed on the Ru-b-Py and on the b-Py ligand show that the lowest energy absorption is due to the population of the triplet state localized on the pyrene-component. Time-resolved studies also evidenced a relatively slow forward triplet equilibration rate, in the order of 2×10 5 s -1 (5 μs), and an even slower back energy transfer rate, 3.3×10 4 s -1 , still faster than the intrinsic decay time of the pyrene (200 μs). [ABSTRACT FROM AUTHOR]

The 2 P state energy of the valence exciton in SrF 2 has been obtained to be 11.1 eV at 298 K through two-photon absorption (TPA) spectroscopy. The luminescence of self-trapped excitons was monitored as the signal of TPA. The exciton binding energy is estimated to be 0.9 eV. This value of binding energy is comparable not only to those obtained through TPA in other alkaline-earth fluorides of CaF 2 and BaF 2 , but also to those of alkali fluorides. The TPA coefficient of SrF 2 was about 5×10 -9  cm/W for 5.55 eV-photons. The value is in the same order of magnitude as those measured at 2 P state of the exciton in CaF 2 and BaF 2 crystals. [ABSTRACT FROM AUTHOR]