Optics and Spectroscopy最新文献

The results of calculating the atmospheric transmission spectrum and modeling lidar signals in the informative range of greenhouse gas sounding (CO₂ and H₂O) on horizontal tropospheric paths using the two-channel infrared lidar system under development are presented. It is shown that the lidar system operation spectral range of 4878–4894 cm^–1 (2043–2050 nm) is preferable for simultaneous probing of CO₂ and H₂O. In this range, the level of lidar signals lies in the range of 10^–6–10^–10 W and exceeds the equivalent power photodetector noise. Based on the results of the calculations, the technical appearance of the developed two-channel infrared lidar system is determined.

The glow of a nanosecond diffuse discharge between two tips with high spatial resolution has been studied. At atmospheric air pressure, as well as at pressures of 300, 100, and 30 Torr, a large number of thin luminous tracks, starting from the region of bright spots on the electrodes, have been discovered. It is shown that the shape of the tracks changes from straight lines to winding ones, and the direction of their movement in some cases changes to the opposite. It is shown that, under conditions of the formation of thin luminous tracks, the bands of the second positive nitrogen system dominate in the emission spectrum of diffuse plasma with a sharply inhomogeneous electric field and nanosecond duration of the voltage pulse. Using an ICCD camera, it has been shown that no emission of the tracks is detected during the first tens of nanoseconds against the background of wide streamers and a diffuse discharge. A hypothesis has been put forward to explain the appearance of numerous tracks during air breakdown in a nonuniform electric field.

A system of differential equations describing the motion of a freely falling body from the point of view of an observer fixed in the center of the standard basis of a specified plane curve and moving together with it has been obtained. Using computer simulation, respective trajectories have been built for two cases: with the observer moving along the circumference either with a constant angular velocity or with an angular velocity varying in accordance with specified laws in the form of a cosine and in the form of a Bessel function.

Using a generalized refractive mixture dielectric model, the influence of the relative permittivity spectra of bound and unbound water in mineral soil on the nature of the temperature dependence of the relative permittivity of natural mineral soil, with a clay fraction content of 41.3%, was studied in the electromagnetic field frequency range from 50 MHz to 15 GHz. The causes of the emergence of intersections in the relative permittivity spectra of mineral soil, obtained at different temperatures but for a sample of the same moisture content, have been studied. It has been proved that the emergence of such an intersection point in the frequency range up to 1.5 GHz is due to the Maxwell–Wagner effect in bound water. The dependences of the frequency of the intersection point of the relative permittivity spectra of mineral soil on the temperature and volumetric content of bound and unbound water have been studied.

Relevance and formulation of the problem. The number of areas of scientific and practical activity in which it is necessary to consider relativistic corrections is steadily growing. In many cases, two objects under study move towards one another. This takes place both in relation to astronomical objects and in relation to quantum particles, including in colliders—accelerators of charged particles in colliding beams. With counter relativistic motions, the relative velocity does not coincide with the approach velocity. However, considering relative velocity alone limits the arsenal of research tools and methods. As opposed to relative velocity, which is determined in accordance with the relativistic formula for velocity addition, the approach velocity of unaccelerated objects is defined as the ratio of the distance between them to the time it takes to cover it. The purpose of this work is to analyze the variety of the relativistic approach velocity of objects depending on the choice of inertial reference frames based on the data of the Large Hadron Collider. Results. At the Large Hadron Collider, the approach velocity of protons is almost twice as high as the speed of light in the laboratory reference frame. In frames of reference associated with moving protons, depending on the options of relativistic transformation of segments of lengths and time intervals, the maximum approach velocity of protons is 1.1 × 10⁸с, and the minimum is 1.2 m/s. In accordance with the technique based on the relativistic velocity addition formula, the approach velocity in reference systems associated with moving protons is almost equal to the speed of light. In this case, the approach velocity becomes equal to the relative velocity, which should not be considered as a generalization of the classical mechanics rule on the indistinguishability of these velocities to relativistic mechanics. Practical significance. The results obtained may be of interest in assessing the approach velocities of astronomical objects, including the Earth and asteroids, as well as significantly expand the variability of hypotheses when processing experimental data arrays obtained at elementary particle accelerators, including the Large Hadron Collider.

The description of photon-matter interaction upon control, transmission, and detection of single-photon, two-photon, and multiphoton states, including the entangled ones, will play an ever-increasing role in many areas of photonics. An appropriate description requires taking into consideration various types of interference effects associated with these states. However, the relatively complex apparatus of second quantization of the electromagnetic field is used even in the simplest single-photon experiments equivalent to the Young’s one, e.g., the experiments with the Mach–Zehnder interferometer. In the present work, the Young’s single-photon mental experiment is explained using the coordinate photon wave function (PWF). The explanation is illustrated by specific examples of the single-photon states at certain wavelengths and different duration of radiation within the framework of two approaches: the quantum mechanical and the “quasi-classical.” In the first approach, a 6-component coordinate PWF is constructed based on the spherically symmetric momentum distribution in a wave packet, followed by approximate analytical calculations. In the second approach, a one-component quasi-classical PWF corresponding to the electric-dipole radiation is constructed. The same pronounced interference pattern was obtained in both cases, which makes is possible to draw the conclusion that the coordinate PWF allows explaining the one- and two-photon interference phenomena. This conclusion sheds the light on theoretical interpretation of the measurement of the coordinate PWF carried out in some of the recent experiments.

The structure and electrical and optoelectronic properties of nanostructured carbon films obtained by methane plasma deposition with subsequent annealing have been studied. It is shown that the film formation conditions affect the final physicochemical parameters. The film morphology has been investigated by atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X-ray energy-dispersive analysis, and analysis of the current–voltage characteristics (CVCs). The film thicknesses range from 20 to 150 nm at the carbon-to-oxygen (C/O) atomic ratio of 4 : 1. Structural studies show that the films obtained consist of nanographite flakes with the lateral dimensions in the range from 5 to 12 nm and contain different fractional concentrations of sp³/sp² crystalline phases of carbon. It is established that the structural quality of carbon films decreases with an increase in the annealing temperature from 650°C to 800°C. At the same time, the degree of graphitization increases, which is indicated by Raman spectroscopy data and sheet resistances calculated from the CVCs. Photocurrents are calculated from the temperature dependences of the CVCs; it is found that the samples exhibit photosensitivity in the temperature range from room temperature to –173°C. These results may be useful for designing day and night light sensors and temperature sensors operating in a wide temperature range.

The defect of the angular momentum of an electron under cyclotron (synchrotron) radiation, including in terms of its spatial orientation, as well as the spatial orientation of the emitted photon, is considered. The possibility of the compatibility of the idea of the photon as a gauge boson, which can exist only in two spin states, ±1, with a linearly polarized photon, i.e., having no spin, has been studied. It is established that photons have no spin. The angular momentum defect can carry away a spinless photon. As applied to the angular momentum defect, the photon momentum arm is equal to its reduced wavelength.

The two-photon interference appearing in a mental experiment similar to the Young’s experiment as a result of simultaneious emission of two photons by (two) independent point sources under the assumption that their radiation is described in the electric-dipole approximation in the classical electrodynamics is simulated within the framework of the photon quantum mechanics by using a six-component photon wave function in the coordinate representation and, for comparison, in the proposed “quasi-classical” approach by using the one-component photon wave function. The relevance of introduction of the photon wave function is emphasized in comparison to the concept of the photon being a “train” of real electromagnetic waves. The task of setting up new experiments that could initiate the analysis of the physical nature of quantum phenomena that occur in the physical vacuum and are formally described by the wave function in the quantum mechanics or by transition amplitudes in the quantum electrodynamics is proposed.

A quantitative analysis technique has been developed, based on multiple regression of Fe–Cr–Mn–Mo–N–C composite steels reinforced with oxide and nitride particles using a BRA-135F spectrometer, to determine the concentrations of chromium, manganese, molybdenum, aluminum, and iron. The problem of the selection of peaks for the analysis at a total content of chromium (11.50–15.03 wt %), manganese (7.56–12.18 wt %), and iron (66.54–74.08 wt %) is considered. Optimal lines of the spectra of the steels under study are proposed to obtain satisfactory results in qualitative analysis with account for the peak overlap. It is shown that due to the overlap of the peaks, chromium should be determined by the peak relating to the CrK_α line; manganese, by the peak relating to the MnK_α line; and iron, by the peak relating to the FeK_β line. An approach to selecting peaks to determine molybdenum concentrations is described. It has been found that due to the absence of a reliable separation of the peaks relating to the MoK_β1 and MoK_β2.5 lines, the molybdenum content should be determined by the peak relating to the line MoK_α. The ingots used as calibration samples were preliminary chemically analyzed to determine the content of metals on an atomic emission spectrometer with the inductively coupled plasma Spectroflame Modula S, which provides high stability and reproducibility of the analysis results in a wide concentration range of elements, including those with a low limit of d-etection. The analysis for determining the concentrations of nitrogen and oxygen in the calibration samples was performed using a METAVAK-VAK analyzer, and the carbon content was determined on a METAVAK CS-30 analyzer.