مجله پژوهش فیزیک ایران
سال بیست و یکم شماره 1 (بهار 1400)

Synchrotron radiation is an advanced polarized and collimated light source with high brilliance and intensity. whereas This radiation has a wavelength range of infrared to the highest-energy x-rays. In this article, we provide a summary of application of x-ray spectroscopy with synchrotron radiation to x-ray spectroscopy. Here we discuss ten types of x-ray techniques include X-ray Powder Diffraction(XRPD), Wide Angle X-ray Scattering (WAXS), Small-Angle X-ray Scattering (SAXS), X-ray fluorescence(XRF), X-ray reflectometry (XRR), Near Edge X-ray Absorption Fine Structure (NEXAFS), X-ray Absorption Near Edge Structure (XANES), Photo Electron Spectroscopy (XPS), X-ray Emission Spectroscopy (XES), and x-ray imaging spectroscopy. These techniques have good potential for characterization of various micro- and nano-materials. Furthermore, some advantages of the use of these techniques are as follows: improving signal to noise ratio, better spatial resolution, and improving data acquisition.

The aim of this study is to investigate dynamical properties of a two-mode f-deformed cavity- field ‎coupled to an effective two-level atom with and without the rotating wave approximation. The first ‎section discusses the theoretical model of the interaction between a two-mode cavity-field and an ‎effective two-level atom within the framework of an f-DJCM without the rotating wave ‎approximation. After that, we obtain the reduced density matrix of the cavity-field with and without ‎the rotating-wave approximation. Then, we have investigated the effect of the counter-rotating ‎terms on temporal evolution of various non-classical properties of the cavity-field, i.e., photon-‎counting statistics, the cross correlation between the modes of the field, and the quantum ‎fluctuations of the quadrature components. Particularly, we compare the numerical result for three ‎different values of the deformation parameter q (q=1, q=1.1, q=0.9) with and without applying the rotating ‎wave approximation. By using of the numerical method, we concluded that even under the ‎condition in which the RWA is considered to be valid, there are the significant effects of virtual-‎photon field on the photon-counting statistics, the cross correlation between the modes of the ‎field, and the quantum fluctuations of the quadrature components‎.

In this study, graphene oxide fibers are introduced as new graphene oxide (GO) membranes with the ‎capability of ion selectivity‏.‏‎ Graphene oxide fibers, like other macro structured membranes, are always ‎associated with cavities and defects. To solve this problem, a 50% combination of graphene oxide ‎suspension including small sheets with an average size of ~ 0.5 µm2 and large sheets with an area of more ‎than 10 µm2 was used. According to the morphological results of scanning electron microscopy, as well as ‎the amount of ionic transport through the fiber, reduction of cavities and its defects were confirmed. ‎Moreover, it was found that ionic current through fibers consist of large and small GO sheets is more ‎controllable. This leads to more ionic selectivity via tunable swelling. Finally, the scalability of graphene ‎oxide fibers investigated and found that increasing number and length of the fibers increases the ionic ‎current as linear trend‎.

Ignoring thermal fluctuations of the environment, taking into account only its dissipative effects, free propagation of a Gaussian wavepacket is studied in the framework of the linear Caldirola-Kanai (CK) equation and non-linear equations, the Schrodinger-Langevin (SL) equation, known as Kostin equation, and the Schuch-Chung-Hartmann (SCH) equation. By a Gaussian ansatz for the probability density one obtains two equations, one for the evolution of the center of the wave packet which is just the classical Langeving equation and one for the evolution of the width of the wavepacket. This last equation has different forms in different approaches having only an analytic solution in the CK and SCH frameworks. Computations show that for a given friction, the width of the wavepacket increases with time in all approaches. In a given time, it reduces with friction in both CK and SL approaches revealing localization effects of dissipation, while has opposite behavior in the SCH approach. Furthermore, energy expectation value and its time-derivative is computed and compared in all approaches. It is shown that the rate of energy is given by the expectation value of momentum field in the SL framework. Finally, transmission of a Gaussian wavepacket from a rectangular barrier is numerically studied in the context of CK and compared to the non-dissipative case. The transmission decreases considerably with the dissipation.

In this paper, the optical bistability in a plasmonic nanoparticle by using the Hydrodynamic model for conduction electrons is investigated. It is shown that the optical bistable threshold, the bistable region and the shape of hysteresis loop are dependent on the permittivity of the surrounding medium, and the composition of plasmonic nanoparticle.

Diffraction in time and early-arrival phenomena will be studied in the context of dissipative systems. This theoretical consideration is done by using the linear scaled wave equation proposed in the framework of Caldirola-Kanai theory for the continuous quantum-classical transition. Two simple but physically important and interesting examples are studied, sudden release from a shutter where transient behaviors (diffraction in time) are seen; and also transmission through a time-dependent parabolic barrier where early-arrival is seen. Calculations show that diffraction in time is a non-classical effect and temporary behaviors are gradually suppressed as the friction increases. Furthermore, early-arrival is seen even in the classical regime. This means that early-arrival is not a non-classical phenomenon. This behavior will be explained by means of scaled trajectories which are just Bohmian trajectories in the quantum regime.

In this paper we study the dynamics of long-range pairing and hopping p-wave superconducting chain after a ‎sudden quench of chemical potential. We have shown that the quantum-classical phase transition occurs ‎when the system is quenched to the critical point and the Loschmidt echo shows perfect periodic oscillations. ‎Moreover we have studied the dynamical phase transition for a quench across the critical point. Our analysis ‎shows that the dynamical phase transition occurs for the cases where the system initially prepared in the ‎massless edge modes. While the system does not show dynamical phase transition when the system is ‎prepared in the massive edge modes, even the quench crossing the critical point‎‎.

One of the successful models in describing the quark phenomenon is the thick center vortex model. In this model, confinement is attributed to the group's non-trivial centers. The non-trivial centers of the gauge group are also the reason of the presence of vortices. Vortices are point-like soliton structures in two dimensions and line like in three dimensions. In this model we need the diagonal generators of the group representations to calculate and plot a quark potential diagram in different representation. It is common to use the tensor method to calculate these diagonal generators, which requires a lot of calculations. In this paper after introducing the thick center vortex model the tensor method is introduced. Then the concept of root and weight diagram in Lie groups is introduced. Using the root and weight diagram an efficient and simple method for calculating the diagonal generators of group representations is presented. The groups studied in this article are SU (2) and SU (3), which can be extended to other groups.

In this paper, the thermodynamic, structural properties and vibrational spectrum of thorium dioxide have been studied using the Density Functional Perturbation Theory (DFPT) and Density Functional Theory (DFT) in the framework of first principles calculations. Quantum espresso software, which is an open source computing code, has been used in order to compute the kohn-Sham equations to obtain the minimum total energy of crystal. The vibrational spectrum of the thorium dioxide was examined along various symmetrical directions, and the results showed the dynamical stability of the crystal system. The quasi-harmonic Debye-Einstein model as implemented in GIBBS2 Code was used to calculate the thermodynamic properties of thorium dioxide at high temperatures and pressures. The simulation results showed that the Debye temperature of thorium dioxide decreased with increasing temperature at a constant pressure and increased with increasing pressure at a constant temperature. Increasing the Debye temperature indicated an increase in the crystal stiffness and the average sound velocity. It was observed that the volumetric thermal expansion coefficient and gruneisen parameter decreased exponentially with increasing pressure at a constant temperature, while increased with increasing temperature at a constant pressure, indicating an increase in heat transfer in the crystal lattice

In this research, silica aerogel was made by sol-gel method with sodium silicate precursor ‎and drying at ambient temperature. The silica aerogel prepared by this method is ‎superhydrophobic. To make it hydrophilic, the sample was heated at 400 °C for 2 h. The ‎structure of the samples was studied using X-ray diffraction, scanning electron microscopy, ‎adsorption and desorption of nitrogen gas. To investigate the hydrophilicity and ‎hydrophobicity of the samples, the water droplet contact surface test was performed. The ‎chemical bonds of the prepared samples were studied using Fourier transform infrared ‎spectroscopy. The overall results showed that the size of the particles and the pores increase ‎and become smaller, respectively when the hydrophilicity of the silica aerogel sample ‎changes to the hydrophobic sample. The angle of contact of the water droplet with the ‎surface of the hydrophobic sample is 170°, while reaches to 51° for the hydrophilic sample‎.

In this paper highly ordered TiO2 nanotube (TNT) arrays were synthesized using potentiostatic anodization of Ti foil for 12 h at voltage of 60 V and used in polymer gel-state dye senisitized solar cells (DSSCs) . To investigate the morphology and optical properties of the TNTs, scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction techniques (XRD) have been used. The average diameter and length of the TNTs were 100 nm and 30 µm, respectively. XRD and Raman measurements indicated the pure anatase phase of TNTs. A polymer poly(methyl metacrylate- co-methacrylic acid) (PMMA-MA) was mixed with a 3-methoxypropionitrile (MPN) based liquid electrolyte to prepare a gel-state polymer electrolyte. The prepared electrolytes containing varied concentrations of PMMA-MA were characterized by electrochemical impedance spectroscopy (EIS). Power conversion efficiency of NT based DSSCs using a polymer gel electrolyte containing PMMA-MA was comparable with that of the corresponding liquid counterpart.

In this paper, the rate equations for a laser diode subject to an optical injection are studied both ‎analytically and numerically. By determining the Hopf and Routh- Hurwitz conditions, the stability ‎boundaries of the laser system have been studied. The stability diagrams have been discussed in terms ‎of detuning and the injection rate for different values of the linewidth enhancement factor.‎‏ ‏Also, we ‎obtain critical relations for the Hopf points that lead to instability in the laser system. It has also ‎shown that obtained relations depend on four parameters: detuning, linewidth enhancement factor, ‎optical injection strength and pumping current‎.

Bell's inequality has made the ability to find nonlocality in what happened by a numerical indicator. CP violation is one of the most important phenomena that occur in nature. It represents asymmetry in the matter and anti-matter in the universe. In this paper, we use a thought experiment to obtain a formalism of Bell's inequality of type CHSH for Majorana neutrino. This inequality is sensible to CP violation.

In this study the nonlinear optical properties of Eosin-B dye nanoparticles were studied using the ‎scanning-fluorescence spectrophotometer and fluorometer method. The nano water droplet in the ‎oil medium is prepared by a combination of hexane and surfactant water, which is painted inside ‎the drop by Eosin-B. The droplet size was studied on a nonlinear refractive index using a 532 nm ‎laser with a scanning power of 80 mW. The results show that the surface effects on the nano-‎droplets cause the droplets to have a larger nonlinear refractive index. This change was due to a ‎decrease in the accumulation of dyes inside the droplet as well as a decrease in the polarity of the ‎drop solvent relative to the water solvent.

The mechanism of a four-level atom confined in a single-mode optical cavity with multiphoton transition is theoretically investigated in the steady-state. The behavior of the atom-cavity system is delineated by the master equation which in order to solve this equation, a set of expected values of a series of operators has been used. To numerically solve this set of coupled expectation values, the matrix continued fractions method is used. How the changes of the physical quantities including the atomic population inversion, mean photon number and second-order correlation function have been studied for any transition. Finally, the process of converting the four-level atom to a three-level one under several specific conditions is discussed for each transition.

The quantum formulation of a physical system is essentially based on the associated creation and annihilation operators. In this article, we introduce these ladder operators for a movement particle on the circle and 2-dimensional sphere by Berezin’s quantization .This approach is derived from the resolution of the unity condition in coherent states. In other words, the coherent states provide a straight forward quantization scheme from a classical state to corresponding quantum state. In this article, we study the coherent states of these systems from heat kernel function point of view.

- In this paper, a method for generating transverse band (UWB) pulses, the basis of which is a large-scale interferometer with a resonator of small silicone rings capable of changing paired configuration, is reported. Single-cycle, dual-bandwidth signals are generated at the time of the Picosecond pulse, and the small ring amplifier is modulated with square and Gaussian electric pulses, respectively. Microwave photonic systems that work with large optical components suffer from large size, high energy consumption, high cost, and vulnerability to environmental disturbances. Therefore, it is highly desirable to assemble the microwave photonic system on a single chip to make it more compact, cheap, and low-consumption. They have a low spectrum. One of its applications is in short-range wireless telecommunications and high power for wireless transmission of large multimedia data. It can also be used in low speed and power mode for IoT applications such as precision internal positioning. Unlike the WiFi or Bluetooth distance estimation, which is based on signal intensity, the bandwidth signal has a very narrow pulse width, similar to the radar pulse, which enables it to estimate the position using pulse forward time and 10 cm accuracy. With an intensified modulator based on silicon photonics, one can very hopefully generate an adjustable microwave signal on the chip.

Thermal quenching as an important and well-known effect in compounds exhibiting thermoluminescence, should be considered in thermoluminescence studies. Among the models describing the thermoluminescence phenomenon, the mixed order kinetic model provides a more realistic description of this behavior. In this work, the Thermal quenching effect is included in the mixed order kinetic model and the new thermoluminescence glow curve deconvolution function is obtained in terms of the maximum intensity and the maximum intensity temperature. The new equation reduces to the known mixed order model by equating the thermal quenching parameter to zero. Also the kinetic parameters of the peak 5 of LiF: Mg, Ti (TLD-100) thermoluminescence dosimeter considering the new equation (with Thermal quenching effect) and the previous equation (without Thermal quenching effect) for different heating rates are determined and the results are compared.

Measurement and determination of gross alpha and gross beta radioactivity in water are important in all societies and countries of the world because of their adiobiological risks and is part of the goals of standards and public health organizations. Liquid scintillation counting technique is one of the best methods for simultaneously measuring alpha and beta-particle-emitting in water. In this technique, due to the overlap of spectra of alpha and beta, evaluation of the alpha and beta interference and the appropriate PSA value is very important for sample counting rate. The purpose of this work is to measure the activity concentration of gross alpha and beta in bottled water and compare them with the allowable limit and international standards. To achieve the goal of this research, the work was carried out in two phases. In phase 1, the alpha and beta interference and the appropriate PSA are obtained using two standard solutions of americium-241 and strontium-90 with activity of 21 and 40 Bq. In phase 2, The 10 bottled drinking water samples from different brands are analyzed using LSC. The results of the sample counting showed appropriate PSA value of 110 for the measurement of gross alpha and gross beta radioactivity in water. The measurement results showed that the gross alpha and beta activity concentrations were 41-62 mBqL-1 and 57-85 mBqL-1 which are below the allowable limit by comparing the standard limits.

Upon semi-analytical and numerical methods, the quasinormal frequencies of dRGT massive black holes under electromagnetic perturbation are calculated and the dynamical stability of these black holes is investigated. The effect of graviton’s mass on the frequencies is investigated and it is shown that the WKB approximation is valid not only for  but also only for low-mass gravitons.