Optics and Spectroscopy (v.121, #2)

Luminescence of dense Ar–Xe–CCl4 gas mixtures with a low CCl4 content upon pumping by fast electrons and uranium-235 fission fragments is studied by spectroscopic methods. It is found that, in a cell with a resonator tuned to the В–Х transition of the XeCl* molecule (λ = 308 nm), the D-state population of the XeCl* excimer molecule (the D–X transition, λ = 235 nm) depends on the B-state population and increases by many times with increasing B-state population of the XeCl* molecule. The stimulated absorption coefficient k = 1.2 × 10–16 of В–Х transition emission of the XeCl* molecule (λmax = 308 nm), which leads to population of the D-state of this molecule, and the coefficient of amplification μ = 2.5 × 10–4 cm–1 of В–Х transition emission of the ХеCl* molecule (λ = 308 nm) are measured upon pumping by uranium- 235 fission fragments with the specific energy input into the gas medium of ~60 mJ/cm3 and a specific power of energy input of about 240 W/cm3.

The mutual effect of metal sample and turboflame in LIBS signal enhancement by M. Ghezelbash; S. J. Mousavi; A. E. Majd; S. M. R. Darbani; H. Saghafifar; A. Maleki (174-180).
The main aim of the present study is to evaluate the mutual effect of copper sample and turboflame in laser induced breakdown spectroscopy (LIBS) signal enhancement. The use of copper sample leads to a signal enhancement in CN (B 2Σ+X 2Σ+) 384.2–388.4 nm molecular transition, N742nm, N744nm, N746nm (a triplet generated by the fine splitting of the 2s 22p 2(3 P)3s–2s 22p 2(3 P)3p transition) and Hα, 656.3 nm (as a flame inductor) atomic lines analysis. Additionally, increase in copper sample temperature with flame can enhance the Cu atomic line intensities (as copper sample inductors). Moreover, in this paper, the comparison between turboflame and alcohol flame on LIBS analysis was studied. LIBS signal intensity variation in a turboflame and turboflame coupled with copper sample at different laser pulse energies indicated that the low laser pulse energy could be compensated by using a copper sample that is coupled with turboflame and improved LIBS signal enhancement. For flames analysis, the use of metal sample in LIBS method is demonstrated to be costeffective, compact, and capable of signal enhancement.

Quantum-chemical calculations of the structure in the ground and lower singlet excited states and the vibrations (in the ground state) of special pair P of photosynthetic reaction center of purple bacteria (RCPb) Rhodobacter Sphaeroides, consisting of two bacteriochlorophyll molecules PA and PB, have been carried out. It is shown that excitation of the special pair is followed by fast relaxation dynamics, accompanied by the transformation of the initial P* state into the P A δ+ P B δ- state (δ ~ 0.5) with charge separation. This behavior is due to the presence of several nonplanar vibrations with participation of the acetyl group of macrocycle PВ in the nuclear wave packet on the potential surface of the P* state; these vibrations facilitate destabilization of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the macrocycle PA and formation of the P A δ+ P B δ- state. The structural transformations in the P* state are due to its linking character in the contact region of the acetyl group-containing pyrrole rings of PA and PB. The transition from the P* state to specifically the P A δ+ P B δ- state is related to the fact that the acetyl group PA is involved in the intermolecular hydrogen bond with amino acid residue HisL168; for this reason, this group and the pyrrole ring linked with it can hardly participate in structural transformations. The electronic matrix element Н 12 of the electron transfer from the special pair in the P A δ+ P B δ- state to a molecule of accessory bacteriochlorophyll ВА greatly exceeds that for the transfer to ВB. This circumstance and the fact that the P A δ+ P B δ- state is energetically more favorable than the P* state facilitate the preferred directionality of the electron transfer in RCPb Rhodobacter Sphaeroides with participation of the cofactors located in its subunit L.

Specific features of photoprocesses in the dye merocyanine 540 and its complexes with water by O. K. Bazyl’; V. A. Svetlichnyi; G. V. Maier (190-199).
The electronic structure and spectral-luminescence properties of the dye merocyanine 540 have been calculated within the framework of the semiempirical quantum-chemical method of partial neglect of differential overlap (PNDO) with spectroscopic parameterization. The trans and cis conformations of the molecule, as well as the trans–cis photoisomerization process, have been considered. The calculation has been performed for an isolated molecule of the merocyanine 540 and its complex with water. The results of the calculation have been compared with the experimental spectral-luminescence characteristics of the molecule in different solvents. It has been shown that there is a good agreement between the calculated and experimental spectra, the nature of the excited states, and photoprocesses.

The influence of sodium nanoparticles and secondary heat treatment conditions on the spectralluminescent characteristics of fluorophosphate glasses with PbSe molecular clusters and quantum dots is studied. Experiments with glasses containing no sodium nanoparticles show that their thermal treatment leads to the formation of molecular clusters with subsequent formation of quantum dots having an intense luminescence. The results of numerical simulation for glasses with sodium nanoparticles shows that heat treatment leads to formation of a sodium fluoride shell on the nanoparticles surface. It is shown that quenching of the luminescence of PbSe molecular clusters and quantum dots takes place in these glasses.

The effect of silver nanoparticles on the photocycle of bacteriorhodopsin of purple membranes of Halobacterium salinarum by V. A. Oleinikov; K. E. Mochalov; D. O. Solovyeva; A. A. Chistyakov; E. P. Lukashev; I. R. Nabiev (210-219).
The effect of silver nanoparticles (AgNPs) that are adsorbed on the surface of the purple membranes of Halobacterium salinarium bacteria on the optical properties and functional peculiarities of the lightsensitive protein bacteriorhodopsin (BR) has been demonstrated for the first time. Two mechanisms of the effect of AgNPs on the protein photocycle have been demonstrated using Raman scattering, giant Raman scattering, flash photolysis, and atomic force microscopy. It has been shown that the nanoparticles in the immediate spatial vicinity of BR fix its photocycle at the stage where it was at the moment of interaction with the nanoparticles. At greater distances, which reach three radii of an AgNPs, they have a weaker effect on BR, under which it retains the ability to be involved in the photocycle, however, has its parameters significantly changed. Thus, in the case of wild-type BR the photocycle accelerates and for the BR-D96N mutant it becomes slower. The data that are obtained could be of significance for creation of such optoelectronic hybrid systems with BR, where the parameters of its photocycle can be controlled using NPs. The results of the study may also be used in the field of nanobioengineering research, which is directed to creation of unique materials with controlled properties for recording and storage of information, energy transformation, and identification and characterization of trace amounts of analytes.

Intensity of visible and IR emission of intracenter 4f transitions of RE ions in Er- and Tm-doped ZnO films with additional Ag, Li, and N impurities by M. M. Mezdrogina; A. Ya. Vinogradov; M. V. Eremenko; V. S. Levitskii; E. I. Terukov; Yu. V. Kozhanova (220-228).
The use of Ag impurity in Er-doped ZnO films deposited by AC magnetron sputtering with a low growth rate has increased the emission intensity at λ = 1535–1540 nm. An increase in the deposition rate and in the temperature of substrates, as well as the use of Li and N+ impurities, led to a considerable increase in the intensity of the line with λ = 376–379 nm in the case of doping with rare-earth ions (Er, Tm), which makes it possible to use this semiconductor for creation of devices for the short-wavelength spectral region. Introduction of additional impurities in Er-doped ZnO films deposited on bulk ZnO crystals with increasing deposition rate and temperature caused an increase in the intensity of the line with λ = 1535–1540 nm. The photoluminescence spectra of ZnO films doped with Tm (ZnO) exhibited intense emission of lines with λmax = 377 nm.

Structure of ZnZrF6 · nH2O (n = 6–2) and ZnZrF6 crystallohydrates according to vibrational spectroscopy data by E. I. Voit; N. A. Didenko; K. A. Gayvoronskaya; A. V. Gerasimenko (229-240).
Fluoridezirconate crystallohydrates ZnZrF6 · nH2O (n = 6–2) and anhydrous ZnZrF6 are investigated by vibrational spectroscopy and thermography. The influence of the hydrate number on the structure of the cationic and anionic sublattices of the crystallohydrates is studied. The changes in the strength of HOH···F and HOH···O hydrogen bonds of coordinated and outer-sphere water molecules occurring with variations in the hydrate number are determined by changes in the IR spectra. The IR spectra of ZnZrF6 · nH2O (n =6, 4) compounds, which have isolated complex anions [ZrF6]2– in their structure, revealed a band with two peaks in the range of 3470–3430 cm–1, which corresponds to stretching vibrations of coordinated water molecules. The spectra of ZnZrF6 · nH2O (n = 5, 3, 2, 1) crystallohydrates with a polymeric structure show a high-frequency shift of this band, which corresponds to weakening of hydrogen bonds. The vibrations of crystallization water molecules involved in the network of strong O–H···F and O–H···O hydrogen bonds manifest themselves in the spectra of ZnZrF6 · nH2O (n =5, 3) crystallohydrates by broad structureless bands in the region of stretching, bending, and libration vibrations.

Optical properties of nonstoichiometric ZrO x according to spectroellipsometry data by V. N. Kruchinin; V. Sh. Aliev; A. K. Gerasimova; V. A. Gritsenko (241-245).
Amorphous nonstoichiometric ZrO x films of different composition have been synthesized by the method of ion-beam sputtering deposition of metallic zirconium in the presence of oxygen at different partial oxygen pressures in the growth zone, and their optical properties have been studied in the spectral range of 1.12–4.96 eV. It is found that light-absorbing films with metallic conductivity are formed at the partial oxygen pressure below 1.04 × 10–3 Pa and transparent films with dielectric conductivity are formed at the pressure above 1.50 × 10–3 Pa. It is shown that the spectral dependences of optical constants of ZrO x films are described well by the corresponding dispersion models: the Cauchy polynomial model for films with dielectric conductivity and the Lorentz–Drude oscillator model for films with metallic conductivity.

Synthesis, spectroscopic investigations, and computational study of 4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde by Ayoub Kanaani; Davood Ajloo; Hamzeh Kiyani; Mohamad Vakili; Mahnaz Farahani; Majid Amiri (246-252).
4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde has been synthesized in an attempt to obtain a new photochromic compound. The optimized molecular structure, mole fractions of title compound in trans and ana forms have been investigated. UV-visible spectra of the compound were also recorded. Upon irradiation with 300 nm light, the camel solid turned orange, in which a visible absorption band was observed at 475 nm. The electronic properties, such as HOMO, LUMO and band gap energies were obtained by the time-dependent DFT (TD-DFT) approach. The predicted nonlinear optical properties of the title compound are much greater than those of urea. Transition structures were calculated by QST3 and IRC methods which yielded the potential energy surface and activation energy.

Modification of porous glass (PG) plates is carried out by impregnation with aqueous solutions of ammonium molybdate (NH4)2MoO4 with subsequent removal of water at 120°C. A long-wavelength shift of absorption spectra upon accumulation of the salt in PG indicates polymerization of MoO 4 2- anions at low concentrations of the encapsulated salt. Photochromism manifests itself as the anionic forms in PG become larger. UV irradiation of the modified plates causes enhancement of continuous absorption in the visible range. The proposed mechanism of photoreduction of the polianions in PG involves the removal of oxygen atoms from the bridging–Mo–O–Mo–bonds and stabilization of the colored forms by means of conjugation of the electrons released from the 4d-levels of pentavalent molybdenum.

The conditions for the onset of modulation instability of wave packets in an optical waveguide in the presence of the traveling refractive index wave are investigated. An expression governing the growth rate of a small harmonic perturbation at the early development stage of the modulation instability is obtained. Based on numerical analysis, the behavior of the wave packet at the developed modulation instability stage is studied for different parameters of the waveguide and the refractive index wave.

Laser-induced synthesis of metal–carbon materials for implementing surface-enhanced Raman scattering by A. Kucherik; S. Arakelian; T. Vartanyan; S. Kutrovskaya; A. Osipov; A. Povolotskaya; A. Povolotskii; A. Man’shina (263-270).
Metal–carbon materials exhibiting surface-enhanced Raman scattering have been synthesized by laser irradiation of colloidal systems consisting of carbon and noble metal nanoparticles. The dependence of the Raman scattering intensity on the material composition and laser irradiation conditions has been investigated. The possibility of recording the Raman spectrum of organic dye rhodamine 6G, deposited in amount of 10–6 M on the substrate obtained from a colloidal solution is demonstrated.

On the possibility of reducing the influence of laser radiation linewidth on execution of quantum logic operations using off-resonant Raman interaction by R. A. Akhmedzhanov; L. A. Gushchin; I. V. Zelensky; V. A. Nizov; N. A. Nizov; D. A. Sobgaida (271-275).
We investigate the possibility of reducing negative influence of the laser radiation linewidth on execution of quantum logical operations using off-resonant Raman interaction.

We have reported the measurement of third-order optical nonlinearity by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique and discussed its usefulness over other popular measuring techniques such as Z-scan, degenerate four wave mixing (DFWM) and third harmonic generation (THG). The measurement has been simulated theoretically by taking different numerical values as well as sign of δ, which is a key parameter of ARINS. The technique has been benchmarked using toluene and the theoretical simulation has been substantiated experimentally by measuring the nonlinear optical coefficients (n 2 and β) of two different samples. The disadvantages of the technique have also been discussed. However, a number of advantages of ARINS override its disadvantages and therefore, ARINS may be preferred over other measuring techniques for the measurement of nonlinear optical parameters.

Band structure and birefringence of LiRbSO4 crystals by V. Yo. Stadnyk; B. V. Andrievskii; L. T. Karplyuk; O. R. Onufriv (283-288).
Theoretical and experimental investigations of the energy-band structure and optical properties of LiRbSO4 crystals of the orthorhombic Pnma phase have been performed. The band structure, density of states, and permittivity distribution ε(E) have been calculated within the electron-density functional theory by the pseudopotential method. Spectral dependences of birefringence Δn і of LiRbSO4 crystals for different crystallophysical directions have been obtained based on these calculation results. The experimental and theoretical birefringence spectra are found to be in good agreement.

An integral modification of the generalized point-matching method (GPMMi) in the electrostatic problem for axisymmetric particles is developed. Scalar potentials that determine electric fields are represented as expansions in terms of eigenfunctions of the Laplace operator in the spherical coordinate system. Unknown expansion coefficients are determined from infinite systems of linear algebraic equations (ISLAEs), which are obtained from the requirement of a minimum of the integrated residual in the boundary conditions on the particle surface. Matrix elements of ISLAEs and expansion coefficients of the “scattered” field at large index values are analyzed analytically and numerically. It is shown analytically that the applicability condition of the GPMMi coincides with that for the extended boundary conditions method (ЕВСМ). As model particles, oblate pseudospheroids $$rleft( heta ight) = asqrt {1 - {^2}{{cos }^2} heta } ,;{^2} = 1 - { aise0.7exhbox{${{b^2}}$} !mathord{left/ {vphantom {{{b^2}} {{a_2}}}} ight.kern- ulldelimiterspace}!lower0.7exhbox{${{a_2}}$}} geqslant 0$$ with semiaxes a = 1 and b ≤ 1 are considered, which are obtained as a result of the inversion of prolate spheroids with the same semiaxes with respect to the coordinate origin. For pseudospheroids, the range of applicability of the considered methods is determined by the condition $${ aise0.7exhbox{$a$} !mathord{left/ {vphantom {a b}} ight.kern- ulldelimiterspace}!lower0.7exhbox{$b$}} < sqrt 2 + 1$$ . Numerical calculations show that, as a rule, the ЕВСМ yields considerably more accurate results in this range, with the time consumption being substantially shorter. Beyond the ЕВСМ range of applicability, the GPMMi approach can yield reasonable results for the calculation of the polarizability, which should be considered as approximate and which should be verified with other approaches. For oblate nonconvex pseudospheroids (i.e., at $${ aise0.7exhbox{$a$} !mathord{left/ {vphantom {a b}} ight.kern- ulldelimiterspace}!lower0.7exhbox{$b$}} geqslant sqrt 2 $$ ), it is shown that the spheroidal model works well if pseudospheroids are replaced with ordinary “effective” oblate spheroids. Semiaxes a ef and b ef of the effective spheroids are determined from the requirement of the particle volumes, as well as from the equality of the maximal longitudinal and transverse dimensions of particles or their lengths. As a result, the polarizability of pseudospheroids can be calculated by simple explicit formulas with an error of about 0.5–2%.

Monte Carlo simulation of aorta autofluorescence by A. A. Kuznetsova; A. E. Pushkareva (304-309).
Results of numerical simulation of autofluorescence of the aorta by the method of Monte Carlo are reported. Two states of the aorta, normal and with atherosclerotic lesions, are studied. A model of the studied tissue is developed on the basis of information about optical, morphological, and physico-chemical properties. It is shown that the data obtained by numerical Monte Carlo simulation are in good agreement with experimental results indicating adequacy of the developed model of the aorta autofluorescence.

Methods for monitoring the optical power of artificial refractive eye lenses (intraocular lenses) based on measuring focal lengths in air and in medium are analyzed. The methods for determining the refraction of diffractive–refractive lenses (in particular, of MIOL-Akkord type), with allowance for the specific features of the diffractive structure, are considered. A computer simulation of the measurement of the focal length of MIOL-Akkord lenses is performed. The effective optical power of the diffractive component of these lenses is shown to depend on the diaphragm diameter. The optimal diaphragm diameter, at which spherical aberrations do not affect the position of foci, is found to be 3 mm. Possible errors in measuring the focal lengths are analyzed, and the necessary corrections that must be introduced into measurement results and calculations of refractions are determined.

Currently dengue fever diagnosis methods include capture ELISAs, immunofluorescence tests, and hemagglutination assays. In this study optical diagnosis of dengue virus infection in the whole blood is presented utilizing Mueller matrix polarimetry. Mueller matrices of about 50 dengue viral infected and 25 non-dengue healthy blood samples were recorded utilizing light source from 500 to 700 nm with scanning step of 10 nm. Polar decomposition of the Mueller matrices for all the blood samples was performed that yielded polarization properties including depolarization, diattenuation, degree of polarization, retardance and optical activity, out of which, depolarization index clusters up the diseased and healthy in to different separate groups. The average depolarized light in the case of dengue infection in the whole blood at 500 nm is 18%, whereas for the healthy blood samples it is 13.5%. This suggests that depolarization index of polarized light at the wavelengths of 500, 510, 520, 530 and 540 nm, we find that in case of depolarization index values are higher for dengue viral infection as compared to normal samples. This technique can effectively be used for the characterization of the dengue virus infected at an early stage of disease.