The infrared transmission and reflection spectra of a series of samples of bismuth films of different thicknesses on identical single-crystal silicon substrates were measured. Transmission and reflection oscillations caused by interference on the film thickness are investigated. Properties of Si-plates are estimated. Refractive index and absorption index of bismuth are calculated.
The processes of the formation of J-aggregates during the dissolution 2,2-difluoro-4,6-di(4'-methylphenyl)-1,3,2-dioxaborine crystals (1) and their subsequent dissociation have been studied by absorption and luminescence spectroscopy and quantum-chemical modeling. It is shown that two luminescent centers are observed in the solution 1: monomeric luminescence and luminescence of J-aggregates (dual luminescence). Evolution of absorption, excitation and luminescence spectra is observed over time, indicating a slow dissociation of J-aggregates.
The paper presents a flux crystal growth technique, studies of the structural peculiarities and the optical absorption spectra of double orthoborate TbCr3(BO3)4 with a huntite structure. The intensities of the phonon modes were used to determine the ratios of the rhombohedral and monoclinic polytypes for this compound, depending on the growth conditions. The broadband absorption spectra of the Tb3+ ions in TbCr3(BO3)4 single crystals were studied in the temperature range from room temperature to 3.0 K. From them, the energies of the crystal-field levels of the Tb3+ ion were determined. The temperature dependence of the absorption spectra of the Er3+ probe ion in TbCr3(BO3)4:Er(1%) shows that there are two phase transitions and agrees with their previously proposed interpretation: at 8.8 K, the chromium subsystem antiferromagnetically orders, and at 5 K, a reorientation of chromium magnetic moments occurs.
We studied the effect of long-term constant light exposure on the severity and reversibility of morphological changes in the liver of laboratory rats. Modeling of light exposure was carried out by means of 24 h exposure to artificial light (in the daytime—300 lk, at night—500 lk). During the study we found that morphological changes in the liver were represented by damage to the parenchyma and circulatory disorders, the degree of which increased with increasing duration of exposure. After providing natural light in the laboratory, gradual recovery of the morphological structure of the organ was observed, which indicates the reversibility of the changes detected.
In order to model the spectroscopic and scattering properties of a quantum system, we propose and explore a new absorbing complex-type optical potential based on a combination of cosine functions. This function provides a high degree of smoothness to joint with a physical real-type potential. The capabilities of this function are investigated in terms of its effect on otherwise freely evolving quantum dynamics. We use our open-source programs to implement the Fourier Grid method with the Optimizer package (in Matlab), freely available at https://sourceforge.net/projects/optimizer-sovkov/.
A brief review of studies of crystals containing metal ions with unfilled f- or d-shells, made in the Institute of Spectroscopy of the Russian Academy of Sciences by high-resolution Fourier spectroscopy, is given. The main directions of study include hyperfine structure in spectra, isotopic effects, the role of random deformations, phase transition spectroscopy, low-dimensional magnets, coupled electron–phonon excitations.
An experimental study of nonlinear absorption process of ultrashort laser pulses in bulk of natural diamond has been carried out. The results of experimental studies on measuring nonlinear transmission of 1 mm thick plane-parallel plate made of diamond irradiated with focused by micro lens (NA = 0.55 with focal length f ' = 5 mm) 0.3 and 10 ps laser pulses with 1030 nm wavelength are presented. It is shown that in this sample the main attenuation mechanism of ultrashort laser pulses with 1030 nm wavelength at intensities not exceeding 10 TW/cm2 is two-photon absorption at color centers, the absorption coefficient β2 = 4.1 ± 0.3 cm/TW is determined.
The effect of adsorption of acid gases CO2, SO2, and SO3 on the electron accepting ability of cations on the surface of calcium oxide was studied by low-temperature IR spectroscopy of adsorbed CO. It is shown that the formation of carbonate, sulfite and sulfate anions in the surface layer leads to the appearance of Lewis acid sites, the strength of which, estimated by the shift in the vibration frequency of CO molecules associated with them, increases in the appropriate order, approaching that for calcium-containing zeolites. The results of the calculation of cluster models by the DFT method confirm the observed trends in the variation of the vibrational frequency and the absorption coefficient of CO molecules bound through both the carbon and oxygen atoms, and also demonstrate the dependence of the ability of a cation for CO linkage isomerism on its local environment.
The temperature-dependent luminescence spectra were analyzed to determine the parameters of the electron–phonon interaction (Huang–Rhys factor and the average phonon energy) for nanocomposites with colloidal CdSe/CdS/ZnS quantum dots (deposited on the surface of a glass substrate and embedded in a thin polymer film of polyisobutylene, and in a frozen colloidal solution in toluene). The measured values of the parameters are analyzed in comparison with model calculations and data obtained using the low-frequency Raman spectroscopy. It is found that in the case of a vitrified colloidal solution of quantum dots in toluene, the matrix effect leads to a noticeable change in the parameters of the electron–phonon interaction.
The current paper demonstrates theoretical analysis of two types of spectral curves for several configurations of system of two-level light emitters, considering the influence of local field and close environment inside a transparent medium. Probe field absorption spectra and resonant fluorescence spectra are calculated under excitation of a strong monochromatic cw laser. The sensitivity of absorption and emission optical spectroscopy method is compared for revealing the effects of the medium on individual emitters and their ensembles. Spectral curves were calculated for model emitters considering local field influence of a transparent dielectric medium and local electron-phonon interactions, which determined the response of the emitters to an external laser field and effective relaxation mechanisms. The calculation formalism is based on a semiclassical approach, while the relaxation processes associated with the phonon contribution are introduced phenomenologically with references to other studies.
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