Том 124, № 4 (2018)

The determination of the matrix elements of single-electron operators for the transitions between electronic states (primarily, the dipole moments of electron transitions) is one of the critical problems in simulating the atomic and molecular spectra. In this study, the efficiency of a simple version of the finite-field method for calculating these values within the Fock-space coupled-cluster theory has been investigated.

Chemical shifts of the K_α1 and K_α2 lines (the 2p_3/2 → 1s_1/2 and 2p_1/2 → 1s_1/2 transitions, respectively) of the X-ray emission spectrum of the Yb atom in fluorides have been calculated by ab initio modeling the electronic structure. The valence transition Yb(II) → Yb(III) has been analyzed by examples of YbF₂, YbF₃, and Yb₂F₄ molecules and YbF₂⁺ cation. The relativistic pseudopotential and basis sets corresponding to it have been constructed for the ytterbium atom. They were used in calculations by the two-component noncollinear version of the density functional theory (DFT) with the PBE0 exchange-correlation functional. Results for the three-coordinated Yb(II) in the FYbF₂YbF dimer demonstrated a very weak dependence of the chemical shift on the coordination number of the Yb atom and on the molecular association of ytterbium difluoride. Chemical shifts of the X-ray emission spectrum for the ytterbium compound are related mainly to the change in the occupation of the 4 f shell.

Chemical shifts of the K_α1 and K_β1 lines of X-ray-emission spectra of niobium in oxides (Nb₂O₅)_n, n = 1–4, relative to metal Nb have been calculated. Stoichiometric clusters (Nb2O5)n the electronic structure of which was calculated using accurate relativistic pseudopotentials and two-component version of the density functional theory are considered as prototypes for modeling different crystal forms of niobium(V) oxide. The chemical shifts were calculated using the method based on using the property of approximate proportionality of valence spinors in the core region of the heavy atom [11]. Corrections to values of chemical shifts have been determined with allowance for deviations from the abovementioned proportionality. Rapid convergence of results with respect to the size of the niobium oxide cluster has been demonstrated.

Results of a comprehensive study of the interface interaction of a nanostructured CuO_x and multiwalled carbon nanotubes (MWCNTs) in CuO_x/MWCNT nanocomposite by X-ray absorption spectroscopy (XANES, NEXAFS) and X-ray photoelectron spectroscopy (XPS) methods using a synchrotron radiation are presented. It is established that a nanostructured CuO_x in CuO_x/MWCNT nanocomposite is predominantly formed by CuO and has the form of flakelike particles 200–500 nm in size uniformly dispersed over an array of nanotubes. A chemical interaction of CuO_x and nanotubes with formation of covalent carbon–oxygen bonds, which does not lead to a significant destruction of the outer layers of carbon nanotubes, is observed at the interfaces of the nanocomposite.

The photolysis of Chicago Blue Sky diazo dye is studied. It is experimentally shown that the presence of metal nitrates in aqueous solutions changes the photolysis mechanism and sharply increases the photolysis rate.

Data in the literature on the optical properties of aluminum in the range of 198–1173 K are analyzed. Analytical expressions describing the dependences of aluminum permittivity on photon energy and temperature are proposed and tested. The spectral dependences of the aluminum absorption coefficient and specular reflectance at normal incidence, as well as of the absorption-efficiency coefficients of aluminum nanoparticles in a lithium-fluoride matrix, are calculated at different temperatures. The results obtained indicate the appearance of unusual nonlinear absorption effects in nanocomposites containing aluminum nanoparticles, which manifest themselves in a decrease in the absorption efficiency with increasing temperature at photon energies exceeding 1.40 eV.

The shape of an optical self-similar pulse that propagates in a medium of finite length with noninstantaneous nonlinear absorption is found analytically. The pulse has an asymmetric shape and, in addition, frequency modulation, which confirms that it belongs to a new type of self-similar propagation modes of laser radiation—chirped pulses with a self-similar shape. The existence of pulses of this kind is also confirmed by results of computer simulation.

The possibility of generation of quasi-unipolar extremely short pulses (with a duration of several periods of field oscillations) is theoretically analyzed for the excitation of a circular, nonlinear, and resonant medium with a light spot. The light spot rotates along a circle with a velocity that exceeds the speed of light in vacuum, while particles of the medium are distributed uniformly along the circle. It is shown that, by introducing a delay in the form of a phase plate into the system, one can control the shape, the duration, and the amplitude of generated pulses.

We have investigated the capabilities of the method of digital speckle interferometry for determining subpixel displacements of a speckle structure formed by a displaceable or deformable object with a scattering surface. An analysis of spatial spectra of speckle structures makes it possible to perform measurements with a subpixel accuracy and to extend the lower boundary of the range of measurements of displacements of speckle structures to the range of subpixel values. The method is realized on the basis of digital recording of the images of undisplaced and displaced speckle structures, their spatial frequency analysis using numerically specified constant phase shifts, and correlation analysis of spatial spectra of speckle structures. Transformation into the frequency range makes it possible to obtain quantities to be measured with a subpixel accuracy from the shift of the interference-pattern minimum in the diffraction halo by introducing an additional phase shift into the complex spatial spectrum of the speckle structure or from the slope of the linear plot of the function of accumulated phase difference in the field of the complex spatial spectrum of the displaced speckle structure. The capabilities of the method have been investigated in natural experiment.

Problems related to determination of refractive indices of layered strongly scattering biological media by means of an optical tomography are investigated. Methods of reconstruction of refractive indices of layers, which are based on the smoothness properties of the solution to the initial-boundary problem, are proposed within the framework of the nonstationary radiative-transfer model. The influence of the probe-pulse duration on the accuracy of recovery of the sought-for characteristics of the medium is investigated numerically.

Results of measurements of particle sizes of a dispersed medium by the methods of laser polarimetry and dynamic light scattering are presented for water suspensions of ZnO, CuO, TiO₂, and BaTiO₃ with particles of irregular shape. When using the laser-polarimetry method, the particle-size distributions within the framework of the spheroidal-scatterer model are reconstructed. The same model was used to correct data obtained by the method of dynamic light scattering. The data obtained are compared with results obtained by electron microscopy. It is shown that, at values of the size parameter of 2–5, correction of the results of measurements obtained by the dynamic-light-scattering method makes it possible to reduce the error in determining the average particle size by this method to no more than 11%.

Analysis and generalization of the results of investigations devoted to the improvement of optical properties have been carried out, and descriptions of a structure and a reaction mechanism of available and promising window glasses with solar radiation are presented. All devices are divided into groups with static constant and dynamic regulated spectral characteristics. The group of static glasses includes heat-protective and spectrally selective glasses with low-emissivity coatings and infrared filters with dispersed plasmonic nanoparticles. Electrochromic glasses, nanostructured dynamic infrared filters, and glasses with separated regulation of the transmission of visible-light and near-infrared radiation are dynamic devices. It is noted that the use of mesoporous films made of plasmonic nanoparticles open up especially wide possibilities. Their application allows one to realize a dynamic separated regulation of the transmission of visible light and nearinfrared radiation in which, under the gradual increase in the electric potential on the glass, mechanisms of plasmon and polaron reduction of solar radiation gradually change the glass’ condition from light warm to light cold and then to dark cold consecutively.

should read “porphyrazine” instead of “porphyrazin”;

should read “intersystem crossing” instead of “intercombinational conversion”;

should read “mirror-symmetrical” instead of “reflection-symmetric”;

should read “fluorescence enhancement” instead of “fluorescence buildup.”

Page 722, Abstract, lines 9–10 from the top, the sentence should read:

This characteristic increases upon tetrapyrrole phenylation.

Page 727, left column, lines 17–18 from the top, the sentence should read:

The vibronic transition parts of the emission spectrum are diffuse, (…)

Page 727, left column, lines 29–30 from the top, the sentence should read:

Note that the Stokes shift in these cases is relatively large.

Page 729, left column, lines 8–10 from the bottom, the sentence should read:

For H₂Ph₈TAC^mp and H₂Ph₆TAC^tm, the enhancement of fluorescence is weaker than in the former case: on cooling, τ_F is increased by a factor of 4–5 in MTHF and by a factor of only 2.6–3 in toluene.

Page 729, right column, lines 9–10 from the footnote, the sentence should read:

It is seen from Table 1 that our results agree reasonably well with previously reported data.

Page 730, left column, lines 16–19 from the top, the sentence should read:

The lifetime for the outgassed H₂TAP solution in

toluene (τ_T⁰) was measured by A.S. Stasheuski as phosphorescence decay at λ_reg = 1070 nm using the setup described in [29].

Page 730, left column, lines 20–23 from the top, the sentence should read:

The τ_T value derived from the kinetics of the rise of singlet oxygen luminescence [26] for the nonoutgassed solution at λ_reg = 1272 nm is 162 ns;

Page 730, right column, lines 25–27 from the top, the sentence should read:

Therefore, for H₂TAP (λ_F⁰⁰≈ 620 nm), the internal conversion probability should not be high.

Page 731, left column, the heading of Table 2 should read:

Bond lengths in the porphine macrocycle (Å).

Page 731, left column, lines 3–6 from the top, the sentence should read:

For elucidating the mechanism of the deactivation of the S₁ state, it was of essential interest to see whether the enhancement of H₂TAP fluorescence would be observed at 77 K.

Page 733, left column, lines 2–3 from the top, the sentence should read:

The corresponding difference for the H₂P–H₂C pair is 0.013 Å.

Page 733, left column, lines 14–16 from the top, the sentence should read:

The macrocycle undergoes additional contraction, and the symmetry of its conjugated system is very close to D_2h.

Page 733, right column, line 21 from the top should read:

Replacement of the methine bridges (…)

Page 734, left column, lines 8–11 from the figure caption, the sentence should read:

This is the main reason of the large bathochromic shift of the Soret band of H₂Ph₈TAP and MgPh₈TAP [16] relative to H₂TAP and MgTAP, respectively.

Page 734, left column, lines 1–4 from the bottom, the sentence should read:

The complete INDO/Sm calculation yields the corresponding quantitative characteristics, which are in good agreement with experimental data (see below).

Page 740, left column, reference no. 25 should read:

25. V. A. Galievsky, A. S. Stasheuski, V. V. Kiselyov, A. I. Shabusov, M. V. Belkov, and B. M. Dzhagarov, Instrum. Exp. Tech. 53, 568 (2010).

25. V. A. Galievsky, A. S. Stasheuski, V. V. Kiselyov, A. I. Shabusov, M. V. Belkov, and B. M. Dzhagarov, Instrum. Exp. Tech. 53, 568 (2010).

30. V. L. Ermolaev and E. B. Sveshnikova, Acta Phys. Pol. 34, 771 (1968).