Communications in Physics

In this paper, we present the results of the preparation of Surface Enhanced Raman Spectroscopy (SERS) substrates by depositing silver nanoparticles (Ag NPs) onto a porous silicon wafer that is produced by the chemical etching process. The influences of the preparation parameters such as resistivity of the silicon wafer, the anodizing current density, etching time to the size of pores were systematically investigated. The SERS substrates prepared were characterised by using appropriate techniques: the morphology and pores size by scanning electron microscope (SEM), the SERS activity by Raman scattering measure of organic molecules malachite green (MG) embedded into the substrate at room temperature. Our experimental results show that a home-made Raman microscope system could be efficiently used to detect the MG molecules at the concentration lower than 10-7 M with the prepared SERS substrates which have Ag NPs in the obtained pores of 10 – 40 nm.

The advent of electromagnetically induced transparency (EIT) offered a new coherent material with exotic and controllable optical properties. Although, studies on single-EIT are described in detail for single-EIT, however, extension from single- to multi- EIT is currently of current interest due to it gains advantages in multi-channel optical communication, waveguides for optical signal processing and multi-channel quantum information processing. In this work, we review recent research works concerning multi-EIT and some related applications, as controlling group velocity of light, giant Kerr nonlinearity, optical bistability. A special attention of the review also gives for analytical interpretations of EIT spectrum, its dispersion and related applications such as EIT enhanced Kerr nonlinearity and optical bistability to give physics insight. From experimental point of view, a latest development for measuring multi-EIT spectrum and its dispersion in hot medium is presented and compared to theoretical analytical representations.

We present a study of the polarization observables of the $W$ and $Z$ bosons in the process \(p p \to W^\pm Z\to e^\pm \nu_e \mu^+\mu^-\) at the 13 TeV Large Hadron Collider. The calculation is performed at next-to-leading order, including the full QCD corrections as well as the electroweak corrections, the latter being calculated in the double-pole approximation. The results are presented in the helicity coordinate system adopted by ATLAS and for different inclusive cuts on the di-muon invariant mass. We define left-right charge asymmetries related to the polarization fractions between the \(W^+ Z\) and \(W^- Z\) channels and we find that these asymmetries are large and sensitive to higher-order effects. Similar findings are also presented for charge asymmetries related to a P-even angular coefficient.

This work is devoted for gauge boson sector of the recentlyproposed model based on \(\mathrm{SU}(3)_C\otimes \mathrm{SU}(3)_L\otimes \mathrm{U}(1)_X\) group with minimal content of leptons andHiggses. The limits on the masses of the bilepton gauge bosons andon the mixing angle among the neutral ones are deduced. Using theFritzsch anzats on quark mixing, we show that the third family ofquarks should  be different from the first two. We obtain a lowerbound on mass of the new heavy neutral gauge boson as 4.032 TeV.Using data on branching decay rates of the \(Z\) boson, we  can fix the limit to the \(Z\) and $Z^\prime$ mixing angle\(\phi\) as \(-0.001\le\phi\le 0.0003\).

The obtainable quality factor for a nano beam resonator is limited due to internal damping such as thermoelastic damping. Therefore, understanding how internal damping varies with the respective resonant modes is very important to design a high performance nanoresonator. In this research, we investigate thermoelastic damping depending on vibration modes of nano beam resonators using finite element method. The study results show that the quality factor of a nanoresonator is lower than at high order modes. The silicon nano beam resonator with the quality factor larger than one million can be achieved by optimizing the dimensions of the resonant beam.

Monoclinic tungsten oxide (WO3) nanoplates were synthesized via a two-step simple process: acid precipitation at room temperature to prepare WO3.H2O nanoplates and annealing at high temperature (400 and 500 oC) in ambient air to obtain WO3 nanoplates. The effect of annealing temperature on physical properties (morphology, oxygen deficiency, crystallinity, optical properties, and photocatalytic activity) of WO3 nanoplates was studied. At both two studied annealing temperatures, all samples have the stable monoclinic structure and visible light-range optical bandgap, but the morphology and photocatalytic activity of the samples vary significantly with annealing temperature. At higher annealing temperature (500 oC), the sample has both nanoplate and nanograin morphologies with round edges, higher crystallinity, larger optical bandgap (2.71 eV), and lower photocatalytic activity. The sample annealed at 400 oC has nanoplate morphology with sharp edges, lower optical bandgap (2.63 eV), and higher photocatalytic which shows a high potential for photocatalytic application under visible light irradiation. The effect of the annealing temperature on the properties of  WO3 nanoplates is assigned to the dehydration, the coalescence, and/or the melting processes at high temperatures. Dehydration causes the formation of oxygen vacancy – oxygen deficiency. The coalescence and/or the melting result in the changing of morphology and the decrease of the oxygen vacancies. These results imply a simple, cost-effective method to prepare highly oxygen-deficient WO3 nanoplates.

Abstract. In this work we report a hydrothermal approach for synthesis of zinc stannate (Zn2SnO4)nanocrystals. Our research focused on the effect of the molar ratio of initial chemicals, reaction temperature and reaction duration on the phase composition and the fluorescence properties.Structural and optical properties of the final products were investigated in detail. X-ray diffractionanalysis indicated that the Zn2SnO4 nanocrystals possess face-centered cubic crystal structure.Raman scattering spectra exhibit two characteristic vibrational modes of Zn2SnO4 crystals. Optical band gap of Eu3+-doped Zn2SnO4 nanocrystals obviously depends on Eu3+content. Theroom-temperature emission spectra of the undoped Zn2SnO4 nanocrystals show two broad bands,while the photoluminescence spectra of Eu3+-doped Zn2SnO4 nanocrystals exhibit the emissionpeaks related to the radiative intra-configurational f-f tr ansitions of Eu3+ions. The absorptiontransitions within Eu3+ions were observed both in the photoluminescence excitation spectra andin the diffuse reflection spectra.

We present new results for the theoretical prediction of doubly-polarized cross sections of $WZ$ events at the LHC using leptonic decays. Compared to the previous studies, two new kinematic cuts are considered. These cuts are designed to enhance the doubly-longitudinal (LL) polarization and, at the same time, study the Radiation Amplitude Zero effect. We found a new cut on the rapidity separation between the $Z$ boson and the electron from the $W$ decay which makes the LL fraction largest, namely $|\Delta y_{Z,e}| < 0.5$. This result is obtained at the next-to-leading order in the strong and electroweak couplings.

It is explicitly shown that either the approximate solution of the integral equation for the inverse of the pion form facto,r or the result of the Pad\(\text{\'e}\) approximant method of resumming the one loop Chiral Perturbation Theory (CPTH) are equivalent to the standard vector meson dominance (VMD) models, using the vector meson coupling to two pseudoscalars given by the KSRF relation. Inconsistencies between the one loop CPTH and its unitarised version (or the VMD model) are pointed out. The situation is better for the CPTH calculation of the scalar form factor and the related S-wave $\pi \pi$ scattering. The branching ratios of \(\tau \to \pi^+ \pi^0 \nu \), \(\tau \to K \pi \nu \), \(\tau \to K^+ \eta \nu\) and $\tau \to K^+ \bar{K^0} \nu\) using only two inputs as the \(\rho\) and \(K^*\) masses, or the two corresponding rms radii, agree with the experimental data. Using the same number of parameters, the corresponding one loop CPTH calculation cannot explain the $\tau$ data.

We argue that dark matter can automatically arise from a gauge theory that possesses a non-minimal left-right gauge symmetry, SU(3)_C \otimes SU(M)_L \otimes SU(N)_R \otimes U(1)_X, for (M,N)=(2,3), (3,2), (3,3), \cdots, and (5,5).