научный журнал по физике Оптика и спектроскопия ISSN: 0030-4034

JIANG Y.S., LI M. — 2014 г.

Micro-Doppler effect is induced by the micro-motion dynamics of the radar target itself or any structure on the target. In this paper, a simplified cone-shaped model for ballistic missile warhead with micro-nutation is established, followed by the theoretical formula of micro-nutation is derived. It is confirmed that the theoretical results are identical to simulation results by using short-time Fourier transform. Then we propose a new method for nutation period extraction via signature maximum energy fitting based on empirical mode decomposition and short-time Fourier transform. The maximum wobble angle is also extracted by distance approximate approach in a small range of wobble angle, which is combined with the maximum likelihood estimation. By the simulation studies, it is shown that these two feature extraction methods are both valid even with low signal-to-noise ratio.

NEFISE CIGDEM YASAYAN, SENAY YURDAKUL, SERDAR BADOGLU — 2014 г.

The mid-IR, far-IR, and Raman spectra of piperidine-3-carboxylic acid were measured and interpreted with support of the MP2 and B3LYP/6-311++G(d, p) calculated harmonic vibrational spectra. 10 stable piperidine-3-carboxylic acid tautomers/isomers were found after B3LYP calculations. The experimental absorption bands of carboxylate (COO-) group show that the free piperidine-3-carboxylic acid molecule exists in zwitterionic form and the most stable tautomer (NAT-1) can be stabilized by an intramolecular N–H···O hydrogen bond. All vibrational frequencies of NAT-1 assigned in detail with the help of total energy distribution (TED). The experimental vibrational wave numbers were compared with the calculated data.

BAIBEKOV E.I. — 2014 г.

An ensemble of N noninteracting spins being in thermal equilibrium and coupled to the resonant mode of a lossless microwave cavity is studied as the function of the spin temperature . Near = 0 the system is known to be in a coupled spin-photon state that manifests itself by the splitting of the cavity mode (vacuum Rabi splitting). The cavity emission spectrum is simulated for arbitrary . A critical temperature C= S /2, where S is the spin excitation energy, is related to the destruction of the strong coupling regime as a consequence of thermal excitations arising within the spin ensemble.

BAOLIANG MA, LIANGSHU WEI, LIPING LU, XIAOSEN LUO, XIAOWU NI — 2014 г.

This paper presents the excitation spectra and fluorescence spectra of mixed solution containing chlorophyll a(Chla), chlorophyll b(Chlb) and -ionone of different concentration, investigates the spectral changes of Chla and Chlb caused by -ionone through optimizing the frontier orbital of Chl- -ionone compound, and calculates the energy transfer rate between Chla and Chlb by means of the fluorescence Gauss decomposition. The results show that the -ionone interacts with Chl mainly via the connection between the magnesium atom in Chl molecule and the carbonyl in -ionone molecule. The formation of Chl- -ionone compound changes the charge distribution of Chl so greatly that it leads to the red-shift of the excitation spectra and blue-shift of the fluorescence spectra of Chls. Also in the compound the electronic energy located on carbon double bond of -ionone can be transferred to Chl molecule by the Mg... O bond, which enhances the fluorescence intensity greatly. The calculation of the excitation energy transfer (EET) rate indicates that a small amount of -ionone can promote the EET between Chla and Chlb.

CUNXIONG ZHU, FENG ZHANG, FENGKAI YANG, NIANWEN CAO, SHAOBO YANG, YINHAI XIE — 2014 г.

This paper presents a new approach that has been developed to identify individual aerosol species using polarization lidar measurements. Individual aerosols can be identified based on their distinct ratios of extinction to backscatter, which are related to the depolarization ratio profile. Aerosol backscatter coefficients can be obtained from these ratios. Differential aerosol backscatter coefficients are proportional to the variation of the ratio of extinction to backscatter coefficient, and the coefficients increase, reach a peak value, and then decrease again, with increasing range.

CUNXIONG ZHU, FENGKAI YANG, NIANWEN CAO — 2014 г.

This paper considers the relationship between the accuracy of aerosol extinction inversion and the boundary value, and derives a theoretical high-accuracy aerosol extinction coefficient inversion. Aerosol extinction coefficient profiles depend on the boundary value. The relationship function of the differential extinction coefficient and differential boundary value is expressed by a maximum value. The smaller the differential boundary value, the smaller the differential extinction coefficient. The clean atmosphere layer is easily found from the lidar range-corrected signal, and the extinction coefficient of the clean atmosphere layer can be obtained using the slope method. By relating the extinction coefficient of the clean atmosphere layer to the extinction coefficient profiles at different boundary values, an accurate aerosol extinction coefficient profile can be obtained.

KHORDAD R., MIRHOSSEINI B. — 2014 г.

In this paper, we have studied optical properties of spherical quantum dots by using Rosen-Morse potential. In this regard, we have first solved the Schrodinger equation and obtained energy levels and wave functions by applying Nikiforov–Uvarov (NU) method. Then, by using density matrix method, we have applied analytical expressions for the linear and third-order nonlinear absorption coefficient and refractive index changes. The results show that, the total refractive index changes and the absorption coefficients increase and shift towards higher by enhancing height potential.

FUGUI YANG, ZHONGCHAO XIA — 2014 г.

In the process of investigating end-pumped continuous intra-cavity Raman laser, a strong blue luminescence at wavelength 473 nm (nanometer) in pure [XO4]2 (X = W, Y... ) has been observed. This luminescence is strange and inconsistent with the traditional single up-conversion luminescence theory, scintillation theory. Basing on the optics theory and scintillation crystal theory, we suggest a “mixing frequency inducing blue emission” mechanism to explain the phenomenon. The mixing wavelength 473.4 nm with the four wavelengths of 808, 890, 912 and 1064 nm stimulates and induces the blue emission of the [WO4]2. The mechanism is in good harmony with the experiment.

LIU CHANGSHI — 2014 г.

The paper is aimed at modeling optical spectra of silicon. Optical spectra of silicon are described with the Logistic function. A satisfactory agreement between the measured and the modeled optical spectra is obtained. The minimum magnitude of the correlation coefficient between experiment and theoretical results is 0.994, and the maximum average relative error is 4.21%. Meanwhile, it is found that the band gap of semiconductor may be determined by fitting absorption coefficient as a function of wavelength. Lastly, the mathematical relationships between the parameters, which are used to link the reflectance of silicon and wavelength, and radiation fluency, are obtained. Consequently, the change of reflectance for silicon can be predicted by both wavelength and dose radiation fluency only one function. All results in this paper are of interest from both optics and materials point of view.

DALIBOR PETKOVIC, MISS LAIHA MAT KIAH, NOR BADRUL ANUAR, PAVLOVIC NENAD T., SHAHABODDIN SHAMSHIRBAND — 2014 г.

The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to estimate MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

DERELI O., ERDOGDU Y., GULLUOGLU M.T., OZMEN A., SAYIN U., SUNDARAGANESAN N., TURKKAN E. — 2014 г.

In the present study, an exhaustive conformational search of the Alpha-benzoinoxime has been performed. The FT-IR spectrum of this compound was recorded in the region 4000 400 cm-1. The FT-Raman spectrum was also recorded in the region 3500 50 cm-1. Vibrational frequencies of the title compound were calculated by B3LYP method using 6-311++G(d,p) basis set. The calculated vibrational frequences were analysed and compared with experimental results.

BAHCELI S., GOKCE H. — 2014 г.

Molecular geometry, experimental vibrational wavenumbers, electronic properties, and quantum chemical calculations of minaprine (C17H22N4O · 2HCl), (with synonym, dihydrochloride salt of N-(4-methyl-6-phenyl-3-pyridazinyl)-4-morpholineethamine) which is widely used as a psychotropic drug at medicinal treatment, in the ground state by using density functional theory (DFT/B3LYP) method with 6-31++G(d, p) basis set have been presented for the first time. The comparison of the observed fundamental vibrational frequencies were in a very good agreement with the experimental data. Furthermore, UV-vis TD-DFT calculations, the highest occupied molecular orbitals (HOMO-1, HOMO), lowest unoccupied molecular orbitals (LUMO, LUMO+1), molecular electrostatic potential (MEP) surface, atomic charges and thermodynamic properties of minaprine molecule have been theoretically calculated and simulated at the mentioned level.

AMALANATHAN M., ERDOGDU Y., GULLUOLU M.T., GUZEL M., HUBERT JOE I., SAGLAM S. — 2014 г.

In this work, FT-IR, FT-Raman, and FT-NMR spectra of 4-Methylesculetin molecule are presented for the first time. FT-IR, FT-Raman and FT-NMR spectra of 4MEC have been recorded and analyzed. The FT-IR and FT-Raman spectra of this molecule are recorded at 4000 400 cm-1 and 50 3500 cm-1, respectively. The infrared vibrational frequencies, absolute intensities, potential energy profile, HOMO-LUMO plot and NBO analysis of the molecule have been also predicted using Beckes three-parameter hybrid B3LYP method in the density functional theory DFT method. Calculated and experimental data are in good agreement.

ESMAEIL DOODMAN, SOHEIL SHARIFI — 2014 г.

Mixtures of oil in water nano-droplets with two molecular weights of a tri-block polymer were studied by quasi elastic light scattering and small angle X-ray scattering. The results showed that, the size and interaction of droplets didnt change with increase of the tri-block polymer length but the order parameters increased. The increase of length of the tri-block biopolymer changed the dynamics of the droplets. A network formation is resulted with increase of the amount of tri-block polymer in the microemulsions.

БЕЗУГЛОВ Н.Н., ЕФИМОВ Д.К., КЛЮЧАРЕВ А.Н., МИЧУЛИС К. — 2014 г.

В рамках аналитической модели и численного моделирования проведено исследование временнй динамики трехмерного атома водорода, находящегося под воздействием внешнего электрического поля. В стационарном случае получены аналитические выражения для определения эволюции момента количества движения L ридберговского электрона (РЭ) и отмечены существенные колебания L. В условиях реализации режима динамического хаоса, стимулированного линейно поляризованным микроволновым полем, с помощью унификации уравнений движения и численных расчетов найдены дополнительные особенности эволюции L. Выявлена роль L в процессах формирования диффузионной ионизации РЭ. й динамики трехмерного атома водорода, находящегося под воздействием внешнего электрического поля. В стационарном случае получены аналитические выражения для определения эволюции момента количества движения L ридберговского электрона (РЭ) и отмечены существенные колебания L. В условиях реализации режима динамического хаоса, стимулированного линейно поляризованным микроволновым полем, с помощью унификации уравнений движения и численных расчетов найдены дополнительные особенности эволюции L. Выявлена роль L в процессах формирования диффузионной ионизации РЭ.

HANIF M., SALIK M. — 2014 г.

We present the optical emission studies of sulphur (S) plasma generated by the first (1064 nm) and second (532 nm) wavelengths of a Q-switched Nd:YAG laser. The target material was placed in front of laser beam in air at atmospheric pressure. The experimentally observed line profiles of neutral sulphur have been used to extract the electron temperature (Te) using the Boltzmann plot method, whereas, the electron number density (Ne) has been determined from the Stark broadening. The electron temperature is calculated by varying distance from the target surface along the line of propagation of plasma plume and also by varying the laser irradiance. Beside we have studied the variation of number density as a function of laser irradiance as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increases as laser irradiance is increased.

GANEEV R.A. — 2014 г.

We review the studies of nanoripples formation on various semiconductor species using ultrashort pulses and different experimental conditions. We present recent studies in this field and discuss the fabrication of 2D periodic nanostructures formed on the surface of semiconductor crystals applying a method of two-beam interference of femtosecond laser. Further, we discuss the short-period ripples formation and present the studies of the semiconductors with different bandgaps potentially suitable for generation of subwavelength nanoripples. We also show the method of formation of the nanoholes and nanodots on the surface of different semiconductors. Ripples formation using different laser parameters and ambient media is analyzed with the objective of identifying conditions of forming short-period nanoripples. Finally, we discuss the formation of extended homogenoous laser-induced periodic surface structures using few-cycle laser pulses.

BAHRAMIYAN H., KHORDAD R. — 2014 г.

In the present work, we have studied numerically the second harmonic generation (SHG) and third harmonic generation (THG) in a cone-like quantum dot. For this purpose, we firstly obtained the energy levels and wave functions of this system. Then, we have used an expression for the SHG and THG by a compact density matrix approach and an iterative procedure. The SHG and THG enhance and shift toward lower energy by increasing the height h and vertex angle . According to the results it is found that the structural parameters have great influence on the THG in this system.

BERKOWSKI M., LISIECKI R., RYBA-ROMANOWSKI W., STRZP A. — 2014 г.

Results of detailed spectroscopic investigation of Sm3+ and Dy3+ ions incorporated in crystal structures of YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5, and (Gd, Lu)2SiO5 are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions 4G5/2 6H7/2 of Sm3+ around 600 nm and 4F9/2 6H13/2 of Dy3+ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 ? 10-20 cm2 for Sm3+ in (Gd, Lu)2SiO5 to 1.17 ? 10-20 cm2 for Sm3+ in LiNbO3. Those for dysprosium-doped crystals range from 0.63 ? 10-20 cm2 for LiNbO3:Dy3+ to 2.0 ? 10-20 cm2 for YAl3(BO3)4:Dy3+. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 and 385 nm combined with relatively strong self-quenching of luminescence.

KHARE A., KSHATRI D.S. — 2014 г.

After the first news on rare earth (RE) doped strontium aluminate (SAO) phosphors in late 1990s, researchers all over the world geared up to develop stable and efficient persistent phosphors. Scientists studied various features of long lasting phosphors (LLP) and tried to earmark appropriate mechanism. However, about two decades after the discovery of SrAl2O4 : Eu2+, Dy3+, the number of persistent luminescent materials is not significant. In this review, we present an overview of the optical characteristics of RE doped SAO phosphors in terms of photoluminescence (PL), thermoluminescence (TL) and afterglow spectra. Also, we refresh the work undertaken to study diverse factors like dopant concentration, temperature, surface energy, role of activator, ets. Simultaneously, some of our important findings on SAO are reported and discussed in the end.