Optics and Spectroscopy最新文献

The contributions of additional Fe-binding sites and heme iron to the experimental spectrum of urea-influenced hemoglobin were evaluated based on theoretical analysis of X-ray absorption spectra. The theoretical Fe K-edge X-ray absorption spectra were calculated for structural models of the supposed additional Fe binding sites and heme. Linear combination fit of theoretical spectra showed that in treated hemoglobin iron ions are more likely to be in the additional Fe-binding sites, which is surrounded by the following amino acids: cysteine-93, histidine-146, and asparagine-94 (Cys93, His 146, Asp 94).

A system for microwave diagnostics of low-temperature non-stationary atmospheric plasma jets is proposed, the principle of operation of which is based on the registration of changing in the quality factor of the main mode of the electric type of a cylindrical microwave cavity resonator. The time dependences of the average volumetric conductivity of a plasma jet of a barrier discharge in a helium flow are measured. The discharge was powered from an alternating voltage source with a frequency of 9 kHz. Such a low frequency of the supply voltage made it possible to distinguish individual pulses of breakdowns of the barrier discharge.

The paper considers a strategy to decrease the error of the two-mode entanglement transformation Controlled-Z by introducing non-Gaussian nodes in the cluster. Non-Gaussian nodes are obtained by using a cubic phase gate. We have shown that this strategy can significantly decrease the transformation error. The considered implementation of the Controlled-Z operation contains a teleportation scheme with the cubic phase gate. We have shown that the correct selection of phases during measurement allows for lower errors than in the initial teleportation protocol with the cubic phase gate and the original teleportation protocol.

The analytical structure, absolute values and angular anisotropy of the triple differential cross section of elastic photon–photon scattering in the field of a multicharged neon-like atomic ion are theoretically predicted.

The combination scattering spectroscopy method investigated strains of the epidermal staphylococcus with hemolytic activity and without hemolytic activity. The main spectral differences of the studied groups are established. Complex analysis was used to estimate hemolytic activity using combined scattering (SR) spectroscopy and mathematical approaches.

A decrease in the gain of the active medium of a nuclear-pumped excimer laser has been experimentally discovered at the B–X- and C–A-transitions of the XeCl* molecule (308, 352 nm), when the Ar‒Xe–CCl₄ medium is pumped with mixed gamma-neutron radiation nuclear reactor. The effect is due to the quenching effect of secondary electrons formed in the active medium of an excimer laser under the influence of instantaneous gamma radiation. The effect increases significantly with increasing gamma radiation flux density, and the loss coefficient can reach values of ~10^–2–2 × 10^–2 cm^–1.

To date, two-qubit quantum logic gates have become an essential part of quantum computing. The study of methods for their implementation is an important practical problem for various quantum optical and information applications. In this paper, we have considered a protocol for multimode quantum non-demolition interaction between an atomic ensemble and multimode light with orbital angular momentum in order to analyze the applicability of this protocol in discrete variables computing. We have developed a multimode interaction Hamiltonian and analyzed the dynamics of field and atomic variables depending on the structure of the driving field. We discuss in detail the procedure for separating qubit noninteracting subsystems on a set of atomic and field modes for various values of the orbital angular momentum of the driving field. Such a procedure helps to reduce the considered protocol to the parallel evolution of two-qubit closed systems.

Abstract

The characteristics of a plasmonic graphene patch antenna of rectangular geometry have been simulated in the CST Microwave Studio 2023 software package. It has been shown that the antenna unique property is an electrically controlled multi-band operation (terahertz (THz) and far infrared (IR) ranges) and changing the radiation pattern (RP) toroidal shape to the multi-beam.

We consider the process of transition of a two-level system to the excited state with subsequent photon emission in the presence of a laser pulse with a high degree of unipolarity. Within the framework of quantum electrodynamics, we obtain analytical expressions for the differential probability of the process depending on the temporal scales of the problem: laser pulse duration, excited-state lifetime, inverse transition frequency, and inverse frequency of the photon emitted. Besides, we calculate the total absorption probability by integrating over the three-dimensional photon momentum and summing over polarizations. We compare the results obtained for unipolar and bipolar (many-cycle) pulses.

The most widely used and applied plasmonic materials, namely silver and gold, has limitations due to their high cost and restriction on the spectral position and shape of the plasmon resonance. This remains true for bimetallic silver–gold nanoparticles. Higher flexibility is required, in particular, for the design of broadband absorbers of light, and for this task the metals other than silver and gold are considered. In this paper we study the optical extinction spectra of alloy and composite nanoparticles containing magnesium and gold. The dielectric properties are calculated within the approximation of independent particles (IPA) based on the electronic structure obtained using density functional theory (DFT) with Hubbard correction (DFT+U). The obtained spectra of optical extinction of magnesium–gold alloy nanoparticles demonstrate that the most sensitive to the composition is the region of wavelengths below 500 nm. Simultaneously, the position of the plasmon resonance predicted by Vegard’s law is higher than obtained from accurate DFT+U based calculations. We managed to describe the experimental optical extinction spectra of the glass sample containing gold and magnesium atoms using the calculated spectra. The results points on the formation of composite nanoparticles with core of Au₃Mg alloy and shell of Au in the considered sample.