Optics and Spectroscopy (v.119, #2)

We have calculated emission spectra of photons and electrons and charge spectra of final ions which are produced by the cascade decay of states created by photoionization of the neon atom near the K-threshold. Calculations have been performed by straightforward construction of cascade decay trees. Branching probabilities have been calculated in the Pauli—Fock single-configuration approximation. We have taken into consideration additional monopole excitations and ejections which accompany the 1s-photoionization process as well as the radiative and nonradiative transitions in the course of cascade. As the energy of excitation photons increases, the spectra of cascade photons and electrons acquire a more and more complicated satellite structure, with the probability of formation of final ions with a higher charges increasing.

Scattering of a photon by an electron of the atom continuous spectrum by A. N. Khopersky; A. M. Nadolinsky; R. V. Koneev; V. A. Yavna (187-190).
The quantum effect of anomalous inelastic scattering of an X-ray photon by an εp-electron of the 1s → εp continuous spectrum of the state of atom photoionization is predicted theoretically. It is established that, in the region of elastic photon scattering by an electron of the continuous spectrum, together with the known contribution of the Thomson component (l = 0), there appears a contribution of the infinite (and countable) number of scattering harmonics l ∈ [1;∞]. As an object of the investigation, the Be atom is taken. The absolute values and shape of the triple differential cross section of the elastic, normal, and anomalous Compton scattering have been obtained.

The advantages of the orthonormal basis set of 2π-periodic Mathieu functions compared to the trigonometric basis set in calculations of torsional states of molecules are substantiated. Explicit expressions are derived for calculating the Hamiltonian matrix elements of a one-dimensional torsional Schrödinger equation with a periodic potential of the general form in the basis set of Mathieu functions. It is shown that variation of a parameter of Mathieu functions allows the rotation potential and the structural function to be approximated with a good accuracy by a small number of series terms. The conditions for the best choice of this parameter are specified, and approximations are obtained for torsional potentials of n-butane upon rotation about the central C-C bond and of its univalent radical n-butyl C2H5C·H2 upon rotation of the C·H2 group. All algorithms are implemented in the Maple package.

Variation of amplitudes of Doppler-free saturated absorption resonances as a result of changes in the gas pressure and power of light waves is studied theoretically and experimentally. The results of the investigation are used for the interpretation of weak satellites of superfine-structure multiplets in the spectrum related to tunnel transitions between energy states of a molecule corresponding to its rotation about equivalent symmetry axes. Relative amplitudes of satellites of the AFE and FEF multiplets of the superfine structure of the SiF4 molecule in the frequency tuning interval of a CO2 laser operating at the P(38) line of the 9.7-µm band are studied experimentally. It is confirmed that the variation of relative amplitudes of the satellites is caused mainly by the fact that the magnitudes of the self-induced transparency of the medium that are created by each light wave for itself are different for the main resonances of the multiplet and for their satellites. The discrepancy between the experimental and theoretical dependences of the relative amplitudes of the satellites upon variation of the gas pressure and power of light waves is analyzed. Based on the discovered discrepancy, it is suggested that molecular collisions with Bennett dip or peak transfer contribute to the formation of satellites of the FEF multiplet. Multiphoton processes participate in the formation of one of the multiplets of the FEF multiplet. It is suggested that the power of the light field partially lifts the ban on transitions participating in the formation of satellites of both studied multiplets. Processing of the experimental curves by the leastsquares method revealed spectrally unresolved satellites within the FEF multiplet, which represent crossover resonances between allowed and forbidden transitions. For these satellites, no additional dependence of the amplitude on the laser power or gas pressure was found. The dependence of the amplitude of these satellites is completely determined by different for the main resonances and satellites magnitudes of self-induced transparency of the medium experienced by each light wave.

Study of the Rb D 2-line splitting in a strong transverse magnetic field with Doppler-free spectroscopy in a nanocell by A. Sargsyan; G. Hakhumyan; A. Tonoyan; P. A. Petrov; T. A. Vartanyan (202-207).
Atomic transitions of 85Rb and 87Rb isotopes in a strong transverse magnetic field with induction of up to 7 kG have been studied experimentally. High spectral resolution is achieved owing to the application of the linear Doppler-free spectroscopy method to a nanometric thin cell with the thickness of L = λ/2 = 390 nm, where λ is the wavelength of laser emission tuned to the resonance with the Rb D 2-line (λ/2-method). It has been observed that the number of atomic transitions in the transmission spectrum of linearly polarized (π) radiation decreases from 64 down to 20 transitions as the field strength increases above B > 5 kG. Four atomic transitions (two of 85Rb and two of 87Rb), which are forbidden in the absence of magnetic field, acquire significant strength in the strong magnetic field. Experimental results are in a good agreement with theory. Several practical applications of alkali-vapor-filled nanometric thin cells have been proposed.

We consider a process in which α-particles after α-decay ionize K-shell of daughter atoms and capture electrons. We first have performed similar calculations for collisions of α-particles with He+(1s) ions. This charge transfer process is studied for the collision energy region 0.04–400 keV. The transition amplitudes are calculated in the impact parameter approximation with the use of the close coupling equations method for a basis consisting of eight molecular states. Total and partial charge-transfer cross sections to the 1s and, for the first time, to the 2s and 2p 0, 2p ±1 states of the He+ ion are obtained. Angular differential cross sections for the elastic scattering and charge-transfer processes are calculated in the eikonal approximation for a wide range of scattering angles for the collision energy of 1 keV. Results of calculations are in an excellent agreement with experimental data.

We propose a new mechanism for transitions of electrons from deep impurity levels to the conduction band under the action of light with photon energy E t smaller than ionization energy Et of the impurity center. Energy deficiency δ = E t ω is covered by the kinetic energy of free electrons in the conduction band.

Spectral and electroluminescent properties of coordination compounds of terbium (III) with ibuprofen (in solid form, chloroform solutions, and polyvinylcarbazole films) by L. G. Samsonova; T. N. Kopylova; K. M. Degtyarenko; N. V. Ponarin; S. B. Meshkova; I. I. Zheltvai (221-228).
Spectral properties of terbium (III) complexes with composition of TbL3DL, where L is an anion of d,l-2-(4-isobutylphenyl)propanoic acid (ibuprofen) and DL is 2,2′-dipyridyl (Dipy), 1,10-phenanthroline (Phen), or triphenylphosphine oxide (TPPO), have been studied in a solid form, chloroform solutions, and polyvinylcarbazole (PVC) films. It has been demonstrated that, in PVC films, occupation of the emitting level of terbium (III) involves the participation of polymer. The emission decay lifetimes of terbium in the chloroform solutions and PVC films have been measured. The possibility of the appearance of electroluminescence of complexes in PVC films has been studied.

Kinetics and luminescence of cadmium sulfide quantum dots in fluorine-phosphate glasses by Zh. O. Lipatova; E. V. Kolobkova; V. A. Aseev (229-233).
Fluorine-phosphate glasses activated with cadmium sulfide quantum dots (QDs) have been investigated. QDs of different sizes (2.8, 3.0, and 3.8 nm in diameter) have been formed as a result of heat treatment near the glass-formation temperature. This variation in the QD size leads to a red shift of the fundamental absorption edge (459 nm) and luminescence band (859 nm). A dependence of the excited state lifetime on the recording wavelength in the range of 450–700 nm is revealed. It is shown that an increase in the QD size from 2.8 to 3.8 nm makes the excited state lifetime longer. The quantum yield increases from 16.3 to 33.7% with an increase in the QD size.

The influence of the temperature and duration of ion exchange in BK7 silicate glass in CuSO4:Na2SO4 melt on the optical properties of the glass surface layers has been investigated. It is shown that ion exchange occurs from the melt according to the Cu2+ ↔ 2Na+ scheme. Cu2+ ions penetrate the sample to a depth of about 1 µm. Reduction of Cu2+ ions near the glass surface gives rise to the Cu+ ↔ Na+ ion exchange in the glass. Measurements of refractive index profiles in the glass sample subjected to ion exchange have revealed the formation of two waveguides in the sample: near the surface and at a depth of more than 3 µm; the second waveguide is formed by Cu+ ions. It is shown that relatively low temperatures and short durations of ion exchange lead to the formation of copper molecular clusters Cu n in glass. An increase of ion exchange temperature and duration leads to decomposition of molecular clusters with formation of Cu2+ ions.

It is experimentally shown that irradiation of silver-containing glasses by nanosecond laser pulses with a wavelength of 248 nm leads to the formation of unstable point defects (having absorption bands in the UV and visible spectral ranges) in the irradiated region and causes the transition of ions and charged molecular silver clusters to the neutral state, which is accompanied by an increase in the luminescence intensity in the visible spectral range. The influence of pulsed laser irradiation is compared with the effect of exposure to cw UV light of a mercury lamp. Some models are proposed to explain the influence of the laser effect on the optical properties of glasses.

Spectral properties of copper halide nanocrystals in glasses of fluorine-phosphate matrix by A. N. Babkina; E. V. Kolobkova; V. V. Golubkov; P. S. Shirshnev; N. V. Nikonorov (243-247).
The absorption spectra of glasses of fluorine-phosphate matrix in the near-UV spectral region have been investigated in the temperature range from 20 to 420°C. It is shown that the absorption bands in this spectral region are exciton absorption bands of copper chloride(I) nanocrystals. Results of X-ray diffraction analysis of the glasses are presented. It is shown that the temperature dependences of the exciton absorption bands of CuCl nanocrystals, obtained upon heating and cooling samples, have a a form of hysteresis.

Ultrashort electromagnetic pulses in graphene with disorder by N. N. Konobeeva; M. B. Belonenko (248-251).
Maxwell’s equations describing an electromagnetic field propagating in graphene with disorder are analyzed. The spectrum of electrons for the graphene subsystem is chosen based on the renormalization group approach. An effective equation governing the vector potential of the electromagnetic field is derived and solved numerically. The dependence of the pulse shape on parameters of the problem is investigated.

A theory of an optical self-induced transparency soliton propagating in a waveguide in the presence of a graphene monolayer is constructed. The perturbation theory based on the inverse scattering problem method is used for obtaining explicit analytical expressions for parameters of the (2π pulse) soliton. It is demonstrated that taking into consideration the effects of conductivity in the graphene monolayer leads to exponential variation of the amplitude (width) of the waveguide-mode soliton during propagation.

Complexified spherical waves and their sources. A review by A. M. Tagirdzhanov; A. P. Kiselev (257-267).
Spherical waves in which one of the coordinates of a source point is complexified are considered. Interest in such exact solutions of the wave equation known as “complex source wave fields,” is stipulated by their Gaussian localization, both in the time-harmonic regime and in the nonstationary case, under a proper choice of the wave form. Since a correct description of the square root occurring in the solution requires the choice of a branch cut, the solution has a jump in the physical space and thus satisfies an equation with a certain source. We study such sources in the physical space for various choices of a branch of the root for the time-harmonic and nonstationary cases. From this point of view, Izmest’ev—Deschamps Gaussian beams, Gaussian wave packets, solutions presented by Felsen and Heyman, Sheppard and Saghafi, Saari, as well as X-waves, are examined.

An ellipsometric method for determining the optical parameters of thin-film coatings with a complex structure by A. A. Tikhii; V. A. Gritskikh; S. V. Kara-Murza; N. V. Korchikova; Yu. M. Nikolaenko; V. V. Faraponov; I. V. Zhikharev (268-272).
A method for taking into account the complex structure of single-layer thin-film coatings, which is formed due to the effect of interfaces between the film and surrounding media, for solving the inverse problem of ellipsometry by a modified Malin—Vedam method is proposed and the features of its application are described. As an example, this method is used to interpret the results of ellipsometric measurements of a close-to-stoichiometric polycrystalline La0.7Sr0.3MnO3 film on a crystalline Al2O3 (LSMO/AO) substrate.

Diffraction divergences of acoustic and optical beams are considered as effects determining the minimum angular size of an image element in acousto-optic filtering of object images. Simple formulas for determining this angular size in the diffraction plane and a perpendicular plane have been obtained in relation to the parameters of an acousto-optic filter. The calculated and experimental data are found to be in good agreement. Analysis of the results obtained indicates that the angular resolution can be increased, the quality of spectral images can be improved, and filters with specified asymmetry of the angular resolution can be designed. Analytical conditions for the existence of a group of acousto-optic filters with symmetric angular resolution, which is important for practical applications, are found; these filters are characterized by equal angular resolutions in two mutually perpendicular planes.

Generation of spiral dislocation of wave front in absorbing nematic liquid crystal by I. A. Budagovsky; A. S. Zolot’ko; D. L. Korshunov; M. P. Smayev; S. A. Shvetsov; M. I. Barnik (280-285).
It is demonstrated that an optical beam acquires a component with spiral dislocation of wave front (optical vortex) due to passage through a layer of homeotropically aligned nematic liquid crystal with light-absorbing admixture. The vortex is formed owing to the heating of liquid crystal and transition to isotropic phase in the irradiated region, which leads to the generation of axisymmetric field distribution of director at the interface of the isotropic channel and nematic liquid crystal.

We have considered transient radiation of a charged particle that moves at a constant velocity perpendicularly to the axis of a regular waveguide filled with an anisotropic magnetodielectric medium. Wave equations and analytical expressions for transverse electric (TE) and transverse magnetic (TM) fields in the waveguide have been found. Energies of transient radiation of the particle moving in a rectangular waveguide have been determined. We have obtained conditions of occurrence, the frequency, and the energy of Vavilov–Cherenkov radiation.

Doppler shift of the modulation frequency of laser radiation scattered by a moving object by V. S. Sobolev; E. N. Utkin; G. A. Kashcheeva; F. A. Zhuravel’; A. M. Shcherbachenko (291-294).
It is shown theoretically and experimentally that the intensity of amplitude-modulated coherent optical radiation scattered or reflected by a moving object carries information about the velocity in the form of the Doppler frequency shift of the modulating harmonic function. Since a photodetector responds to the radiation intensity proportional to this function, the above-indicated effect allows one to carry out contactless measurements of motion parameters without using methods of interferometry.

A rapid and non-invasive bio-photonic technique to monitor the quality of onions by H. Ullah; F. Hussain; E. Ahmad; M. Ikram (295-299).
We present the use of swept source optical coherence tomography and spectral domain optical coherence tomography for imaging the skins and concentric tissue leaves of intact whole onion bulb as well as single leave. The normal and watery scaled (defective) onion’s outer leaves and whole bulb have been characterized by cross sectional imaging of internal defects. The method can be used as potential investigating technique for application of food quality check during long storage.

Variation of optical characteristics of polarized laser radiation in dielectric upon its low-frequency rotation and heating by V. O. Gladyshev; D. I. Portnov; S. V. Sadovnikov; V. L. Kauts; E. A. Sharandin (300-305).
The results of experiments in which coherent laser radiation with wavelength λ = 0.632991 µm experienced rotation of its plane of polarization, beam deviation, and change of intensity after propagating through an optical disk made of TF3 glass with refractive index n = 1.71250 and glued to a gyromotor, are discussed. The experiments were conducted at angle of incidence of the beam on a flat surface of the optical disk v = 60°. The rotational frequency of the disk was varied from 2 to 10 Hz for two directions of rotation. At low speed of rotation, the main factor causing mechanical deformations and, as a result, changes in optical characteristics of radiation propagated through the optical disk is heating of the metal—glass interface.

Neodymium laser with negative feedback: Suppression of self-mode-locking, control of mode-locking regime by M. V. Kozlova; A. M. Smirnov; R. M. Al-Khuzheyri; V. N. Mantsevich; V. S. Dneprovskii (306-310).
A simple way of suppression of self-mode-locking in a nanosecond Q-switched Nd3+:YAlO3 laser by placing an element introducing a negative feedback into the laser cavity, which consists of a plate of singlecrystal GaAs exhibiting two-photon absorption (complete suppression) or a cell containing colloidal solution of CdSe/ZnS quantum dots (partial suppression), is implemented. Placing the element introducing the negative feedback into the cavity of a pulsed picosecond mode-locked Nd3+:Y3Al5O12 laser allowed an increase in the number of pulses in the pulse train and a change in the energy distribution between the pulses. Specificities of laser oscillation regimes in the presence of a nonlinear absorbing element in the cavity were analyzed by numerically solving the set of balance equations describing the population inversion density and the photon flux density in the cavity.

A method of fast building of locally equidistant distributions of geometrical objects of illumination systems by D. D. Zhdanov; A. D. Zhdanov; I. S. Potemin; V. Yu. Venediktov; V. A. Galaktionov (311-317).
We have considered general principles of the calculation of lightguiding illumination systems with scattering microstructures and proposed a highly efficient method of building of locally equidistant distributions of microgeometrical objects with a specified density. The developed technique makes it possible to eliminate the Moiré effect in illumination systems with LED lighting. The algorithm of the method has been described. The work is illustrated by examples of calculation of illumination systems of a LC display.

A sensitive spectrofluorimetric method was developed for the determination of famciclovir in pure and pharmaceutical preparations. The method is based on the derivatization reaction of famciclovir with fluorescamine. The different experimental parameters that affect the fluorescence intensity were carefully studied, at once. The method was validated for linearity, limit of detection, limit of quantification, precision, accuracy, recovery, robustness. The assay was linear over the concentration range of 100 and 1000 ng/mL. The limits of detection and limit of quantification were calculated to be 51.13 and 153.39 ng/mL. The proposed method was applied to study of famciclovir in pure and in pharmaceutical preparations.

A selective and sensitive spectrofluorimetric method was developed and validated for the determination of cilazapril in human plasma urine, in pure and pharmaceutical preparations. The proposed method is based on derivatization using 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) as fluorogenic agent and measuring the fluorescence of the products at emission wavelengths of 503 nm after excitation at 374 nm. The method was validated for linearity, limit of detection, limit of quantification, precision, accuracy, recovery. The calibration curves were linear over a concentration range of 100–500 and 50–250 ng/mL for plasma and urine, respectively. The limits of detection were calculated to be 0.26 and 31.59 ng/mL for plasma and urine, respectively. The proposed method was applied to study of cilazapril in pure, human plasma, urine, and pharmaceutical preparations.

Light output and fluorescence efficiency of polymer layers containing colloidal semiconductor phosphors based on CdSe/CdS/ZnS quantum dots by S. A. Pavlov; V. V. Krikushenko; E. M. Antipov; N. B. Voronets; E. Yu. Maksimova; N. E. Sherstneva; S. L. Koryakin (327-331).
Fluorescent polymer films and coatings are coming into use in various fields of engineering and agriculture. New prospects are opened by a new class of phosphors, namely, semiconductor colloidal systems based on CdSe/CdS/ZnS. One of the most effective applications of fluorescent films is their use as light-converting cover materials in agriculture.