Optics and Spectroscopy (v.122, #3)

The probabilities of radiative electric dipole transitions 2p 53p, 2p 6–2p 53s, and 2p 53d in the spectrum of neon-like copper Cu XX and 5p 56p, 5p 6–5p 56s, 5p 57s, and 5p 55d in the spectrum of xenon-like lanthanum La IV are calculated. The wave functions of the intermediate coupling were found from the wellknown experimental energy levels by the least-squares method (LSM). To transfer to an absolute scale the radial integrals for the transitions calculated in the form of a length on the Hartree–Fock functions have been used. By summing the calculated probabilities of the transitions, the lifetimes of the levels of configurations 2p 53s, 2p 53p, and 2p 53d in the spectrum of Cu XX and levels of configurations 5p 56s, 5p 56p, and 5p 57s in the spectrum of La IV have been obtained.

It is shown that laser generation is possible in principle upon coherent excitation according to the V-scheme of the (1s2p)3 P j levels with j = 1, 2 of a helium atom from the (1s2s)3 S 1 level of the same atom when the latter level is, in turn, populated by electron or proton impact.

A systematic study of the dependences of information inequalities relating the variance, Fisher information, and Shannon entropy power in the coordinate and momentum spaces (the Cramér–Rao, Stam, Bialynicki–Birula–Mycielsky–Beckner, and other inequalities) on the vibrational quantum number of a diatomic molecule is performed for the first time. These dependences are calculated for the ground electronic state of the 7Li2 molecule using the semiempirical data available in the literature on the many-parameter potential curve of this state. Specific features of these dependences have been analyzed, their essentially nonmonotonic behavior was revealed, and not only quantitative, but also qualitative, distinctions between these dependences were observed. These results were compared with the results of our calculation in the classical mechanics approximation, and significant (up to a factor of 3.5) discrepancies between these data were observed not only for low-lying, but also for highly excited vibrational levels that are close to the dissociation limit. The results obtained can be used in quantum informatics, analysis of an intramolecular structure and the interaction processes involving the vibrational states of diatomic molecules.

The one-photon transition probabilities in hydrogen-like ions are calculated for nuclear charge numbers in the range 1 ≤ Z ≤ 100. The calculations are performed in the framework of the relativistic Dirac’s theory for the states with the principal quantum numbers n = 2,3, 4. The finite nuclear size effect is taken into account. The role of the quantum electrodynamics (QED) and nuclear recoil corrections is also considered.

Quantum-mechanical calculations of the intensity distribution in the resonance Raman spectrum of an aqueous solution of phenylalanine, excited by light with wavelengths of 193, 204, 218, and 235 nm, and in the nonresonant Raman spectrum excited at a wavelength of 488 nm have been performed. The calculation results are in satisfactory agreement with the experimental data in the literature. Spectral lines characteristic of phenylalanine are observed, which can be used as markers when analyzing the peptide structure. It is noted that the contribution of highly excited electronic states (spaced by less than 10 eV from the resonant lines) to the scattering tensor components must be taken into account. The important role of the Herzberg–Teller effect in the description of spectral intensity distribution is demonstrated.

The influence of temperature on the optical properties of gold nanoparticles by A. V. Kalenskii; A. A. Zvekov; M. V. Anan’eva; A. P. Nikitin; B. P. Aduev (402-409).
The optical properties of gold nanoparticles in a transparent matrix are studied at temperatures from 300 to 1000 K within the spectral range from 450 nm to 1.5 μm. It is shown that, in the case of small nanoparticles and short wavelengths in the plasmon resonance band, an increase in temperature leads to a decrease in the absorption efficiency factor. The light absorption efficiency factor of gold nanoparticles with a radius exceeding 40 nm increases with increasing temperature in the entire spectral range studied. The single scattering efficiency factor always decreases with increasing temperature. The effects observed are related to a change in the refractive indices of gold and the matrix with comparable contributions. It is shown that results of calculations agree qualitatively with available experimental data. The results are necessary to optimize the composition of the actuators, including gold nanoparticles, in the transparent matrices.

The optical constants of a series of ore minerals (pyrite, magnetite, and chalcopyrite) have been analyzed in the microwave range using the Kramers–Kronig method. The spectral dependences of the reflectance of these minerals in a wide frequency range (from deep UV to microwave) have been plotted based on numerous experimental data from different sources. These dependences made it possible to calculate the optical constants of the minerals under study in a frequency range of 12–145 GHz and compare them with the results of the theoretical and laboratory studies published in different sources.

UV radiation dosimeter with double spectral conversion by D. I. Chernakov; A. I. Sidorov (416-419).
The possibility of double spectral conversion of UV radiation from the spectral range of 240–280 nm to the visible spectral region using luminescent glasses and fibers with antimony ions and molecular silver clusters is shown. Planar and fiber prototypes of UV radiation dosimeters are tested. It is shown that the sensitivities of dosimeter of the first and second types are 1400 and 360 mV/W/m2, respectively.

Temperature dependent surface and spectral modifications of nano V2O5 films by M. Aslam Manthrammel; A. Fatehmulla; A. M. Al-Dhafiri; A. S. Alshammari; Aslam Khan (420-425).
Nanocrystalline V2O5 films have been deposited on glass substrates at 300°C substrate temperature using thermal evaporation technique and were subjected to thermal annealing at different temperatures 350, 400, and 550°C. X-ray diffraction (XRD) spectra exhibit sharper and broader characteristic peaks respectively indicating the rearrangement of nanocrystallite phases with annealing temperatures. Other phases of vanadium oxides started emerging with the rise in annealing temperature and the sample converted completely to VO2 (B) phase at 550°C annealing. FESEM images showed an increase in crystallite size with 350 and 400°C annealing temperatures followed by a decrease in crystallite size for the sample annealed at 550°C. Transmission spectra showed an initial redshift of the fundamental band edge with 350 and 400°C while a blue shift for the sample annealed at 550°C, which was in agreement with XRD and SEM results. The films exhibited smart window properties as well as nanorod growth at specific annealing temperatures. Apart from showing the PL and defect related peaks, PL studies also supported the observations made in the transmission spectra.

The results of the spectroscopic NMR (1H, 13C, and 195Pt), infrared, optical, and voltammetric characteristics of the mixed-ligand complexes of Pt(II) and Ir(III) with metalated 2-phenylbenzothiazole and tert-butylisocyanide (tBuNC), acetonitrile (AN), ethylenediamine (En), O-ethyldithiocarbamate (Exn), and diethyldithiocarbamate (Dtc–) ions are presented. It is demonstrated that the change in donor–acceptor interaction of ligands tBuNC, AN, En, Exn, and Dtc with metal leads to an increase in the energy of the highest occupied molecular orbital of the complexes and is accompanied by a shift of the cathode potential of the metal-centered oxidation, a bathochromic shift of the spin-allowed and spin-forbidden metal-tocyclometalated ligand optical charge transfer transitions, and an increase the degree of mixing of the 1MLCT and triplet intraligand states, responsible for the phosphorescence of the complexes.

Surface enhanced Raman scattering by a new derivative of acridine in solutions of colloidal silver by E. V. Solovyeva; D. A. Khaziyeva; L. A. Myund; A. S. Denisova (435-439).
A new derivative of acridine, 4,5-bis(N,N-di(2-hydroxyethyl)iminomethyl)acridine (BHIA), which is a selective fluorophore relative to cadmium cations, is studied by the method of surface-enhanced Raman scattering (SERS). The SERS spectra of BHIA adsorbed on colloidal silver particles exhibit a high intensity and temporal stability of the signal. An assignment of the bands present in the studied spectral range is given. The dependence of the SERS spectra of BHIA on the solution’s pH reveals that the ligand can exist on the surface in protonated and deprotonated forms. The stability of the deprotonated form on the surface suggests that the ligand interacts with the surface by means of a conjugated π-system of aromatic rings. The addition of the salt of halide ions to the solution has a significant influence on the SERS spectrum. This effect is due to the displacement of the adsorbate molecules from the first monolayer, which is accompanied by the transition of BHIA from the chemi- to the physisorbed form.

Electro-optical studies of the dispersion of the polarizability of colloidal diamond particles in water-salt solutions by A. V. Voitylov; V. V. Voitylov; S. A. Klemeshev; M. P. Petrov; A. A. Trusov; V. N. Shilov (440-446).
The dispersion of the electro-optical effect in polydisperse hydrosols of diamond is studied in the external field frequency ranging from 10 Hz to 2.5 MHz. The conservative dichroism, which is determined by the difference in the turbidity constants for light polarized along and perpendicular to the particle-orienting field, is chosen as the electro-optic effect. The dispersion dependences of the dichroism are determined and used to calculate the dispersion of the average values of the polarizability anisotropy of the diamond particles. The influence of the concentration of monovalent ions in an aqueous KCl solution on these dispersion dependences is studied. The experimental dependences of the dispersion are compared with the theoretical ones within the model of the polarizability of the colloidal particles which takes into account the polarizability of the diffuse part of their double electric layer.

The influence of cysteamine and counterion concentrations on the properties of CdSe/ZnS quantum dots by I. G. Motevich; N. M. Popko; N. D. Strekal’; S. A. Maskevich (447-451).
The influence of the cysteamine surfactant concentration on the stability of CdSe/ZnS nanoparticles (NPs) solubilized by this compound at the phase interface between two immiscible liquids is considered. The steady-state and time-resolved fluorescence spectroscopy data show that the fluorescence quantum yield of cysteamine-coated NPs and their stability to aggregation in a potassium phosphate buffer are determined by the balance between the concentrations of surfactant in the aqueous phase and hydrophobic NPs in the nonpolar phase (chloroform, toluene, etc.). It is found that the brightest and most stable hydrophilic NPs can be obtained by completely coating them by cysteamine molecules without a surfactant deficit or excess in the reaction at the phase interface.

Fluorescence and picosecond induced absorption from the lowest singlet excited states of quercetin in solutions and polymer films by S. L. Bondarev; S. A. Tikhomirov; O. V. Buganov; V. N. Knyukshto; T. F. Raichenok (452-461).
The spectroscopic and photophysical properties of the biologically important plant antioxidant quercetin in organic solvents, polymer films of polyvinyl alcohol, and a buffer solution at pH 7.0 are studied by stationary luminescence and femtosecond laser spectroscopy at room temperature and 77 K. The large magnitude of the dipole moment of the quercetin molecule in the excited Franck–Condon state μ e FC = 52.8 C m indicates the dipolar nature of quercetin in this excited state. The transient induced absorption spectra S 1S n in all solvents are characterized by a short-wave band at λ abs max = 460 nm with exponential decay times in the range of 10.0–20.0 ps. In the entire spectral range at times of >100 ps, no residual induced absorption was observed that could be attributed to the triplet–triplet transitions Т 1Т k in quercetin. In polar solvents, two-band fluorescence was also recorded at room temperature, which is due to the luminescence of the initial enol form of quercetin (~415 nm) and its keto form with a transferred proton (550 nm). The short-wave band is absent in nonpolar 2-methyltetrahydrofuran (2-MTHF). The spectra of fluorescence and fluorescence excitation exhibit a low dependence on the wavelength of excitation and detection, which may be related to the solvation and conformational changes in the quercetin molecule. Decreasing the temperature of a glassy-like freezing quercetin solution in ethanol and 2-MTHF to 77 K leads to a strong increase in the intensity (by a factor of ~100) of both bands. The energy circuits for the proton transfer process are proposed depending on the polarity of the medium. The main channel for the exchange of electronic excitation energy in the quercetin molecule at room temperature is the internal conversion S 1S 0, induced by the state with a proton transfer.

Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties by N. Kh. Ibrayev; B. R. Ilyassov; D. A. Afanasyev (462-468).
Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

Formation of channel optical waveguides in polymethylmethacrylate with embedded electro-optic chromophore DR13 by the photoinduced bleaching method by V. I. Sokolov; A. S. Akhmanov; I. M. Asharchuk; I. O. Goryachuk; K. V. Khaydukov; M. M. Nazarov (469-474).
A composite polymeric material based on polymethylmethacrylate (PMMA) with embedded electro- optical (EO) chromophore DR13 is designed. Irradiation with electromagnetic radiation in the visible range leads to a bleaching of the composite and its refractive index n decreases due to the irreversible photodestruction of the chromophore. Changes in the absorption spectrum and refractive index of the composite with the irradiation time are measured. It is shown that the change in n depends on the concentration of DR13 in the polymer matrix and can reach a value of Δn = 0.034 in the telecommunication C-range near a wavelength of 1.55 μm. The rate of bleaching depends on the wavelength of the actinic light and reaches its maximum when the wavelength is near the maximum of chromophore absorption. With the use of the photobleaching method and the PMMA/DR13 composite, channel waveguides and the other elements of the integrated optical devices are fabricated, including waveguide splitters, directional couplers, and Mach–Zehnder interferometers. This simple one-step method does not involve the removal of polymer material by liquidphase or reactive ion etching.

Generation of a sequence of frequency-modulated pulses in longitudinally inhomogeneous optical waveguides by I. O. Zolotovskii; V. A. Lapin; D. I. Sementsov; D. A. Stolyarov (475-481).
The conditions for the generation and efficient amplification of frequency-modulated soliton-like wave packets in longitudinally inhomogeneous active optical waveguides have been studied. The possibility of forming a sequence of pico- and subpicosecond pulses from quasi-continuous radiation in active and passive optical waveguides with the group-velocity dispersion (GVD) changing over the waveguide length is considered. The behavior of a wave packet in the well-developed phase of modulation instability with a change in the waveguide inhomogeneity parameters has been investigated based on the numerical analysis.

The size and shape distributions of particles of a dispersive medium are retrieved from measurements of the scattering matrix for aqueous suspensions of copper and zinc oxides by solving the optimization problem for the sum of the squared deviations of the experimental values of matrix elements and their values calculated using the model of spheroidal scatterers. It is shown that for dispersive media with particles of irregular shapes and with sizes corresponding to the size parameter of 0.1–2, the retrieved distribution has a distortion expressed in an increased fraction of smaller sized particles.

An ellipsoidal model for small nonspherical particles by V. G. Farafonov; V. B. Il’in; V. I. Ustimov; A. R. Tulegenov (489-498).
We have proposed an ellipsoidal model (ElM) for small nonspherical particles, i.e., we have proposed a method to construct “effective” ellipsoids the light scattering properties of which are similar to those of original particles. It has been shown that the semiaxes of a model ellipsoid should be determined from the requirement of equality of the volumes of particles, as well as of the equality of the ratios of their maximal longitudinal and transverse dimensions. Along with the ElM, the uniform internal field approximation (UFA) has also been considered, which is the first approximation in terms of the rigorous ЕВСМ solution of the electrostatic problem. In order to analyze the applicability of the ElM and UFA approximate approaches, rigorous methods for solving the problem of light scattering have been used, such as the discrete dipole approximation (DDA) and the SVM. The comparison of results of numerical calculations for parallelepipeds, finite circular cylinders and cones, Chebyshev particles and pseudospheroids has shown that the relative errors of calculations of the particle polarizability using ElM approximate formulas do not exceed 1–5%, while, for the absorption and scattering cross sections, they are roughly twice as large, since they depend on the squared polarizability module. As a rule, the ElM is preferable to the uniform field approximation, which is advantageous only in the case of a circular cylinder with close longitudinal and transverse dimensions.

We demonstrate the process of adaptive self-visualization of small-scale transparent objects and structures in weakly absorbing optical glasses (a glass plate made of K8 and an NS-1 neutral density filter) placed in the Fourier plane of the optical system under the conditions of thermal self-action of the illuminating laser beam. The process is based on the ideology of the classical Zernike phase contrast method. The process is implemented at the level of power of radiation of the illuminated object varying from several milliwatts to tens of watts in the visible and IR spectral ranges. The conducted experiments indicate that the visualization takes place in all glasses and optical elements fabricated from them at an appropriate level of the radiation power.

Spectral-kinetic characteristics of luminescence of tetranitropentaeritrite with inclusions of iron nanoparticles upon an explosion induced by laser pulses are measured with high temporal resolution. It is shown that the luminescence occurring during exposure to the laser pulse is a result of initiating a chemical reaction in tetranitropentaeritrite and is chemiluminescence. The glow is presumably associated with the excited nitrogen dioxide, NO2, which is formed by the rupture of O–NO2 bond in the tetranitropentaeritrite molecule.