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The objective of the paper was to compare values of the muzzle brake efficiency coefficient for a rifle with active or inactive automatics systems. Special laboratory stand designed for investigating the recoil process was used. The motion of the rifle was detected by the use of the laser interferometer and the optical camera. The recoil velocity time courses were determined by smoothing and differentiation of experimental position records. The results of the experiments indicated that in the case of an active automatics system two values of the recoil velocity can be used for calculation of the energetic efficiency coefficient: the maximum recoil velocity and the final recoil velocity at the end of the automatics action cycle. The values of the coefficient, calculated using these two values of the recoil velocity, distinctly differ. However, it was shown that their values indicate the same relation between the efficiency of various muzzle brakes. The value of the efficiency coefficient, determined on the basis of the final recoil velocity value, is practically the same as that determined on the basis of the final recoil velocity value for the rifle with an inactive automatics system.

We study the quantum interference between the excitation pathways in a three-level $\Lambda$-type atom interacting with two short laser pulse trains under the conditions of electromagnetically induced transparency. The probability amplitude equations which describe the interaction of a three-level $\Lambda$-type atom with two laser pulse trains are numerically solved. We derive analytical expressions for the population of the upper excited state for resonant laser pulse trains with a rectangular temporal profile. By varying the parameters of the laser pulse trains such as area of a single pulse, detuning, repetition period, and number of individual pulses, we analyze the quantum interference between the excitation pathways in terms of the upper excited state population.

In the centre of mass frame, we have studied theoretically the Z -boson resonant production in the presence of an intense laser field via the weak process e + e − → μ + μ − . Dressing the incident particles by a Circularly Polarized laser field (CP-laser field), at the first step, shows that for a given laser field’s parameters, the Z - boson cross section decreases by several orders of magnitude. We have compared the Total Cross Section (TCS) obtained by using the scattering matrix method with that given by the Breit-Wigner approach in the presence of a CP-laser field and the results are found to be very consistent. This result indicates that Breit-Wigner formula is valid not only for the laser-free process but also in the presence of a CP-laser field. The dependence of the laser-assisted differential cross section on the Centre of Mass Energy (CME) for different scattering angles proves that it reaches its maximum for small and high scattering angles. At the next step and by dressing both incident and scattered particles, we have shown that the CP-laser field largely affects the TCS, especially when its strength reaches 1 0 9 V . c m − 1 . This result is interpreted by the fact that heavy interacting particles require high laser field intensities to affect the collision’s cross section.

Anapole states in isolated, homogeneous and isotropic dielectric spheres are studied theoretically in accordance with Mie theory, numerically by full-wave electromagnetic simulations and by measurements at microwave and millimeter-wave frequency. Depending on size and material properties of the dielectric spheres, the practical limitations of detection and possible applications of non-radiating anapole states are investigated. The electromagnetic signature, generated by anapole states of a spherical dielectric scatterer, in terms of finite extinction cross-section, is verified by measurements, for both its electric and magnetic versions, in Silicon and Alumina spheres, respectively. In addition, the existence and the detection of higher-order and hybrid anapole states are demonstrated. Finally, an approach to engineer electric field hotspots in a subwavelength-sized gap between two magnetic anapole coupled Alumina ceramic spheres is demonstrated.

The fundamental concepts and principles of mechanics, or dynamics, were established in the 17th century. Copernicus gave the notion of reference system in 1543, and Galileo stated the principle of inertia in 1638 in his important work Discorsi e dimostrazioni mathematiche intorno a due nove scienze alla meccanica ed i movimenti locali.1 A particle on which no force is exerted has a constant velocity. Linear uniform motion is a state relative to the observer, and not a process. It is the variation of the velocity that is a process resulting from an external action. Many scientists participated in this evolution, such as Tycho Brahe, Kepler, Descartes, and Christiaan Huygens, to name a few.

In this chapter, we look at the energy of electrons in an atom and determine how the quantum state of the atom changes over time. This leads us to introduce the energy operator, or Hamiltonian, and the Schrodinger equation that governs the behaviour of quantum systems. We show how light can interact with an atom, and as a demonstration of the quantum theory developed so far we explain how atomic clocks work.

We theoretically study the influence of laser polarization in inelastic scattering of electrons by hydrogen atoms in the presence of a circularly polarized laser field in the domain of field strengths below $10^{7}$ V/cm and high projectile energies. A semi-perturbative approach is used in which the interaction of the projectile electrons with the laser field is described by Gordon-Volkov wave functions, while the interaction of the hydrogen atom with the laser field is described by first-order time-dependent perturbation theory. A \textit{closed analytical solution} is derived in laser-assisted inelastic electron-hydrogen scattering for the $1s \to nl$ excitation cross section which is valid for both circular and linear polarizations. For the excitation of the $n=2$ levels simple analytical expressions of differential cross section are derived for laser-assisted inelastic scattering in the perturbative domain, and the differential cross sections by the circularly and linearly polarized laser fields and their ratios for one- and two-photon absorption are calculated as a function of the scattering angle. Detailed numerical results for the angular dependence and the resonance structure of the differential cross sections is discussed for the $1s \to 4l$ excitations of hydrogen in a circularly polarized laser field., Comment: arXiv admin note: text overlap with arXiv:1509.08695

We investigate the long-range, two-body interactions between rubidium and potassium atoms in highly excited ($n=70$) Rydberg states. After establishing properly symmetrized asymptotic basis states, we diagonalize an interaction Hamiltonian consisting of the standard Coulombic potential expansion and atomic fine structure to calculate electronic potential energy curves. We find that when both atoms are excited to either the $70s$ state or the $70p$ state, both the $\Omega=0+$ symmetry interactions and the $\Omega=0-$ symmetry interactions demonstrate a deep potential well capable of supporting many bound levels; the size of the corresponding dimer states are on the order of 2.25 $\mu$m. We estabish $n$-scaling relations for the equilibrium separation $R_e$ and the dissociation energy $D_e$ and find these relations to be consistent with similar calculations involving the homonuclear interactions between rubidium and cesium. We discuss the specific effects of $\ell$-mixing and the exact composition of the calculated potential well \textit{via} the expansion coefficients of the asymptotic basis states. Finally, we apply a Landau-Zener treatment to show that the dimer states are stable with respect to predissociation., Comment: 8 pages, 4 figures, 4 tables

Significant progress has been made in recent years demonstrating an all-optical high sensitivity Radio Frequency (RF) sensor exploiting the Electromagnetically Induced Transparency (EIT) effect in an atomic vapor. In order to exploit the potential of these Rydberg RF receivers in practical telecommunications applications, it is necessary to operate these devices outside of a sophisticated optics laboratory and to use rugged components in a noisy environment. We present a simple analytic model for the operation of a sensitive Rydberg RF receiver to predict the optical modulation in response to an RF signal. We show that the optical modulation depth can be maximized using an optimum coupling intensity. The optical modulation depth drops off rapidly as the RF source is detuned away from resonance. By detuning the coupling frequency to compensate for the RF detuning we demonstrate that the useful RF bandwidth of the receiver can be significantly extended. We measure this variation in optical response using a Rubidium vapor at a 15GHz RF carrier frequency. Using readily available optical components we obtain good agreement with our model. This convenient analytic approach will simplify the design and operation of Rydberg RF receivers as sensitive components in future 5G mobile communications, particularly for the power-limited uplink from mobile device to base-station.

A semi-analytical dimensionless formula is presented for predicting the period-one frequency of an optically-injected laser over a wide range of injection powers and positive detunings. The result shows that for any given injected optical power, there exists an optimal detuning at which the period-one frequency is maximized. The formula is applied to a tabletop optical injection system with a commercially-available quantum-well distributed feedback laser with previously unknown design parameters. By extrapolating the linearity of the period-one frequencies at zero-detuning and weak-injection regimes, the physical control parameters of the laser are approximated to the analytical formula for wide ranges of injection powers and positive detunings. The accuracy of the model is experimentally verified, achieving period-one frequencies as high as 84.7 GHz.

Large scale atom interferometers promise unrivaled strain sensitivity to midband (0.1 - 10 Hz) gravitational waves, and will probe a new parameter space in the search for ultra-light scalar dark matter. These atom interferometers require a momentum separation above 10^4 \hbar k between interferometer arms in order to reach the target sensitivity. Prohibitively high optical intensity and wavefront flatness requirements have thus far limited the maximum achievable momentum splitting. We propose a scheme for optical cavity enhanced atom interferometry, using circulating, spatially resolved pulses, and intracavity frequency modulation to overcome these limitations and reach 10^4 \hbar k momentum separation. We present parameters suitable for the experimental realization of 10^4 \hbar k splitting in a 1 km interferometer using the 698 nm clock transition in 87Sr, and describe performance enhancements in 10 m scale devices operating on the 689 nm intercombination line in 87Sr. Although technically challenging to implement, the laser and cloud requirements are within the reach of upcoming cold-atom based interferometers. Our scheme satisfies the most challenging requirements of these sensors and paves the way for the next generation of high sensitivity, large momentum transfer atom interferometers., Comment: 24 pages, 6 figures

The nonlinear effects in optical resonators give a promise for the generation of new laser sources. Here, a whispering gallery mode(WGM) micro-rod resonator is fabricated and the mechanism of transmission between Kerr comb to Raman comb is investigated by experimental results and amended Lugiato-Lefever equation(LLE) model. We show that, numerically and experimentally, the WGM resonator-based optical frequency comb can be selectively accessed from Kerr comb state to Kerr-Raman state via pump and detuning controlling. When the detuning is initially set at red detuning, by simply increasing the pump power, the comb state can lock to the stable Raman soliton comb. This indicates the Raman soliton comb is easier to generate compared to the Kerr soliton comb in silica-based WGM resonator. We wish the experimental results demonstrated here can be used for broadband comb applications.

Measurements of cross-sections of charge exchange between hydrogen atoms and low energy protons (down to the energy ~10 eV) revealed a noticeable discrepancy with previous theories. The experimental cross-sections were systematically slightly higher—beyond the error margins—than the theoretical predictions. In the present paper, we study whether this discrepancy can be eliminated or at least reduced by using the Second Flavor of Hydrogen Atoms (SFHA) in calculations. We show that for the SFHA, the corresponding cross-section is noticeably larger than for the usual hydrogen atoms. We demonstrate that the allowance for the SFHA does bring the theoretical cross-sections in a noticeably better agreement with the corresponding experiments within the experimental error margins. This seems to constitute yet another evidence from atomic experiments that the SFHA is present within the mixture of hydrogen atoms. In combination with the first corresponding piece of evidence from the analysis of atomic experiments (concerning the distribution of the linear momentum in the ground state of hydrogen atoms), as well as with the astrophysical evidence from two different kinds of observations (the anomalous absorption of the redshifted 21 cm radio line from the early universe and the smoother distribution of dark matter than that predicted by the standard cosmology), the results of the present paper reinforce the status of the SFHA as the candidate for dark matter, or at least for a part of it.

A charged filament stretched along the axis of a linear electrodynamic trap performs an oscillatory-rotational motion, as a result of which the charged particles are captured by the filament in the regions of the antinodes. Such a dynamic thread is actually an additional trap inside the Paul trap.

Laser cooling exploits the physics of light scattering to cool atomic and molecular gases to close to absolute zero. It is the crucial initial step for essentially all atomic gas experiments in which Bose-Einstein condensation and, more generally, quantum degeneracy is reached. The ongoing development of laser-cooling methods has allowed more elements to be brought to quantum degeneracy, with each additional atomic species offering its own experimental opportunities. Improved methods are opening new avenues, for example, reaching Bose-Einstein condensation purely through laser cooling as well as the realization of continuous Bose-Einstein condensation. Here we review these recent innovations in laser cooling and provide an outlook on methods that may enable new ways of creating quantum gases., 13 pages, 4 figures

The magnetometer is a multi-parameter system, parameters optimization is always the problem to improve the sensitivity of the atomic magnetometer. Multiple parameters hardly decide the optimized conditions in the experiments because of the influence of several parameters and parameters may interact with each other. Besides, the influence of parameters on the signal-to-noise ratio can hardly be analyzed theoretically due to the complex physical configuration. We used a generalized polynomial chaos expansion to construct an agent model for the SERF atomic magnetometer to replace its complex physical model, and used a variance-based sobol method to perform a global sensitivity analysis of the parameters in this paper. The mathematical method of uncertainty quantification is used to comprehensively analyze six parameters’ effect on SERF atomic magnetometer performance. The results show that the probe laser power has the greatest impact on the atomic magnetometer, and it is the parameter with the highest degree of linearity with the atomic magnetometer. In accordance with the results of the uncertainty quantification analysis, the parameters of the probe laser power of the SERF atomic magnetometer were experimentally optimized, and the performance of the magnetometer was significantly improved.

We have theoretically and experimentally studied the regime of beatings of counterpropagating waves in a Zeeman ring laser under the action of strong fields of ring permanent magnets on the active medium. We have for the first time calculated and measured the dependences of the frequency bias and the intensity of counterpropagating waves of such a laser on the lasing frequency detuning relative to the frequency of the gain line centre. We have revealed some features in the dependence of the frequency bias on the magnetic field strength, associated with the nonlinearity of the active medium polarisability in strong inhomogeneous magnetic fields.

Under the condition of low illumination, the traditional sky screen has low detection ability, which cannot meet the detection and test needs of dynamic projectile’s parameter in weapon field. In order to solve this problem, this paper proposes a design method of laser photoelectric detection target with array lens and high-power line laser, this method mainly uses the high-power line laser to form a fan-shaped laser light source with a certain thickness, and combines the fan-shaped laser light source plane and the receiving detection screen plane to form a laser detection screen. The array meso-lens is introduced to design the laser detection screen of receiving optical path with wide-angle. A high sensitivity array photodetector is used to capture the laser reflection information of projectile when it passes through the laser detection screen. According to the characteristics of the designed laser detection screen, this paper studies the calculation method of laser reflected energy of projectile, establishes the calculation model of laser reflection power of projectile and derives the signal-to-noise ratio calculation function of laser photoelectric detection target. Through the experimental test, the results show that compared with the traditional sky screen, the field of view of the designed laser photoelectric detection target is significantly increased, and the signal-to-noise ratio of the photoelectric detection is significantly higher than the traditional sky screen in low illumination environment.

Nonradiating sources of energy realized under a wave scattering on high-index dielectric nanoparticles have attracted a lot of attention in nano-optics and nanophotonics. They do not emit energy to the far-field, but simultaneously provides strong near-field energy confinement. Near-field wireless power transfer technologies suffer from low efficiency and short operation distance. The key factor to improve efficiency is to reduce the radiation loss of the resonators included in the transmitter and receiver. In this paper, we develop a wireless power transfer system based on nonradiating sources implemented using colossal permittivity dielectric disk resonator and a subwavelength metal loop. We demonstrate that this nonradiating nature is due to the hybrid anapole state originated by destructive interference of the fields generated by multipole moments of different parts of the nonradiating source, without a contribution of toroidal moments. We experimentally investigate a wireless power transfer system prototype and demonstrate that higher efficiency can be achieved when operating on the nonradiating hybrid anapole state compared to the systems operating on magnetic dipole and magnetic quadrupole modes due to the radiation loss suppression. © 2021 Esmaeel Zanganeh et al., published by De Gruyter, Berlin/Boston.

Ultra-narrow clock transition of ytterbium atoms has enabled not only quantum metrology but also quantum simulation of various quantum phenomena. One of such examples is a new possibility of realizing dissipative open quantum systems with minimal heating by optical pumping through the clock transition. Nevertheless, the access to the clock transition and relevant optical pumping often requires a complex laser system. Here we delineate a simple design and characterization of a home-made clock laser system that is capable of driving ytterbium clock transition at 578 nm. A fundamental laser at 1156 nm based on a quantum dot gain chip in a long external cavity configuration seeds the standard bow-tie cavity and generates up to 45 mW power of frequency-doubled yellow light at 578 nm. We have stabilized the laser frequency to a high-finesse ULE (ultra-low expansion) cavity via electronic feedback to the current. We examine the atomic spectroscopy at the clock transition in fermionic $$^{173}$$ Yb atoms, which would allow us to implement controlled dissipation with minimal heating. With the clock laser system built in this work, we envision exploring non-Hermitian physics in various platforms including spin-orbit-coupled fermions and topological bands.

Quantum computers have the potential to advance material design and drug discovery by performing costly electronic structure calculations. A critical aspect of this application requires optimizing the limited resources of the quantum hardware. Here, we experimentally demonstrate an end-to-end pipeline that focuses on minimizing quantum resources while maintaining accuracy. Using density matrix embedding theory as a problem decomposition technique, and an ion-trap quantum computer, we simulate a ring of 10 hydrogen atoms without freezing any electrons. The originally 20-qubit system is decomposed into 10 two-qubit problems, making it amenable to currently available hardware. Combining this decomposition with a qubit coupled cluster circuit ansatz, circuit optimization, and density matrix purification, we accurately reproduce the potential energy curve in agreement with the full configuration interaction energy in the minimal basis set. Our experimental results are an early demonstration of the potential for problem decomposition to accurately simulate large molecules on quantum hardware. Problem decomposition methods may help to overcome the size limitations of quantum hardware and allow largescale electronic structure simulations. Here, a method to simulate a ten-atom Hydrogen ring by decomposing it into smaller fragments that are amenable to a currently available trapped ion quantum computer is demonstrated experimentally.

Increased interest in research of non-linear resonant interactions of waves in rotating astrophysical plasma has taken place in recent years. This is due to the discovering solar magneto-Rossby waves and the emergence of new data on the effect of three-wave interactions of magneto-Rossby waves on solar activity. In context of large-scale magnetohydrodynamic flows in presence of rotation, magneto-Poincaré waves and magneto-Rossby waves are highlighted. The β-plane approximation is developed to simplify the theory of spherical Rossby waves. Nevertheless, the representation of the Coriolis force in this approximation contains a latitude-independent term that ensures the existence of magneto-Poincaré waves on β-plane along with magneto-Rossby waves. In this paper, it is shown that they satisfy the phase matching condition, which leads to emergence of new non-linear interactions mechanisms of waves: two magneto-Poincaré waves and one magneto-Rossby wave; two magneto-Rossby waves and one magneto-Poincaré. Complete dispersion equations on β-plane in quasi-two-dimensional magnetohydrodynamic approximation is analysed both for homogeneous and stratified astrophysical plasma with vertical magnetic field. New dispersion relations for magneto-Poincaré waves on β-plane are obtained. Detailed qualitative analysis of the phase matching condition is carried out, and new types of three-wave interactions of magneto-Poincaré waves and magneto-Rossby waves are found. Three-wave interactions are studied and instabilities of the decay and amplification type are investigated.

As a result of the reactions of cold nuclear transmutation, more energy is released than is expended. To explain the phenomenon, a heuristic algorithm for the chain reaction of string condensation is proposed. The resulting atomic collapsar catalyzes the reactions of cold nuclear transmutation due to the magnetic monopole effect.

In this paper, the principle of forming the spatial distribution of the potential in multipole three-dimensional ion traps of a general type is considered. A matrix method for describing the electric fields in ion traps for the [Formula: see text]th order of multipole is proposed. Typical electrode geometries for hexapole and octupole traps are considered.

In this paper, we report the existence of Eckhaus instability in laser cavities with harmonically swept filters, of which Fourier Domain Mode Locked (FDML) laser is an important example. We show that such laser cavities can be modeled by a real Ginzburg Landau equation with a frequency shifting term arisen from the cavity dispersion. We analytically derived a solution of the governing equation and analyzed its stability. We found that the cavity dispersion introduces a continuous frequency shift to the laser signal such that it will be eventually pushed outside the stable region and trigger the Eckhaus instability. We show that the repeated triggering of the Eckhaus instability in the laser cavities is the dominant effect that leads to the high frequency fluctuations in FDML laser output, which is the unique feature of such laser cavities and intrinsically limits the signal quality of the FDML lasers with nonzero cavity dispersion.

In this paper, we derive a simplified formula of electric dipole moments (EDMs) of a fermion. In the Standard Model, it is well-known that non-trivial cancellations between some rainbow-type diagrams induced by $W$ boson exchanges occur in the calculation of the neutron EDM at the two-loop level due to the gauge symmetry. The fermion self-energy and the vertex correction are related through the Ward-Takahashi identity, and this relation causes the exact cancellation of the EDM. We derive EDM formulas for a more general setup by introducing the form factors for the fermion self-energy and the vertex correction so that the derived formulas can be applicable to a larger class of models. We conclude that the non-zero EDM contributions are induced from rainbow-type diagrams with the chirality flipping effects for internal fermions. We also discuss the other possible generalization of the EDM calculation which is applicable to the other classes of models., 23 pages, 7 figures, 2 tables, the version published in JHEP

A distributed Bragg reflector (DBR) laser represents a simple realization of a semiconductor laser operating in a single longitudinal mode. We present a so far missing theoretical study how its reflection tolerance depends on the detuning between lasing wavelength and maximum of the DBR reflectivity. The generic Lang-Kobayashi equations for lasers subject to optical feedback are extended to include the detuning parameter on base of the round-trip condition for stationary states. As a consequence, a well established formula for estimating the feedback tolerance is modified for detuned DBR lasers, too. Bifurcation analysis of the Lang-Kobayashi equations confirms the modified formula. Properly adapting the parameters of the DBR, the calculations yield a possible tolerance of the simple DBR laser against nearly 100 % feedback.

Neutral atoms are promising for large-scale quantum computing, but accurate neutral-atom entanglement depends on large Rydberg interactions which strongly limit the interatomic distances. Via a phase accumulation in detuned Rabi cycles enabled by a Rydberg interaction of similar magnitude to the Rydberg Rabi frequency, we study a controlled-phase gate with an arbitrary phase and extend it to the controlled-NOT gate. The gates need only three steps for coupling one Rydberg state, depend on easily accessible van der Waals interaction that naturally arises between distant atoms, and have no rotation error in the weak interaction regime. Importantly, they can work with very weak interactions so that well-separated qubits can be entangled. The gates are sensitive to the irremovable fluctuation of Rydberg interactions, but can still have a fidelity over 98\% with realistic position fluctuation of qubits separated over 20~$\mu$m., Comment: 7 pages, 3 figures

The phenomenon of stimulated Raman scattering (SRS) of elliptical q-Gaussian laser beams interacting nonlinearly with underdense plasmas has been investigated theoretically. Using variational theor...

In this work the nonrelativistic ionization energies 3He2+μ−e− and 4He2+μ−e− of helium-muonic atoms are calculated for S states.The estimates are based on the variational principle of exponential expansion. Convergence of the numerical values of variational energies is studied by increasing a number of the basis functions N. That allows to claim that the obtained energy values have 30-33 significant digits for S states

Universal control of multiple qubits—the ability to entangle qubits and to perform arbitrary individual qubit operations1—is a fundamental resource for quantum computing2, simulation3 and networking4. Qubits realized in trapped atomic ions have shown the highest-fidelity two-qubit entangling operations5–7 and single-qubit rotations8 so far. Universal control of trapped ion qubits has been separately demonstrated using tightly focused laser beams9–12 or by moving ions with respect to laser beams13–15, but at lower fidelities. Laser-free entangling methods16–20 may offer improved scalability by harnessing microwave technology developed for wireless communications, but so far their performance has lagged the best reported laser-based approaches. Here we demonstrate high-fidelity laser-free universal control of two trapped-ion qubits by creating both symmetric and antisymmetric maximally entangled states with fidelities of $${1}_{-0.0017}^{+0}$$ and $${0.9977}_{-0.0013}^{+0.0010}$$ , respectively (68 per cent confidence level), corrected for initialization error. We use a scheme based on radiofrequency magnetic field gradients combined with microwave magnetic fields that is robust against multiple sources of decoherence and usable with essentially any trapped ion species. The scheme has the potential to perform simultaneous entangling operations on multiple pairs of ions in a large-scale trapped-ion quantum processor without increasing control signal power or complexity. Combining this technology with low-power laser light delivered via trap-integrated photonics21,22 and trap-integrated photon detectors for qubit readout23,24 provides an opportunity for scalable, high-fidelity, fully chip-integrated trapped-ion quantum computing. Laser-free universal control of two trapped-ion qubits using a combination of radiofrequency and microwave magnetic fields achieves some of the highest fidelities ever reported for two-qubit maximally entangled states.

The notion of the electric dipole polarizability density function of atoms and molecules has been considered. The current density induced by the time derivative of the electric field of monochromatic light allows for a new definition of the electric dipole polarizability density, which is translationally invariant. This translational invariance provides the physical meaning that was lacking in previous defined polarizability densities. The new polarizability density has been implemented at the TD-DFT level of theory. The origin independence has been proven in silico to hold regardless of the basis set size. Two emblematic molecules, i.e., CO and N2, which in many respects display similar electric response, have been studied in detail. The substantial differences, which have been highlighted in the topology of the parallel and perpendicular polarizability density tensor components of CO and N2, are grossly hidden by compensation, when integration is carried out to get the molecular properties.

Visible Laser Light Communication System (VLLC) is a wireless communication system, using laser as the medium. In the data transfer process, it is possible to have optical interference where 2 laser beams coincide with one point on the reflector. Research on the effect of laser source interference has been carried out by several researchers including mitigation actions to reduce its effects. This experiment uses 2 optical distance sensors that produce a laser with a wavelength of 650 nm with a power

We report a measurement of the photoionization cross-section of the lithium 2P3/2 state in a magneto-optical trap (MOT) by means of a single-frequency cw laser. Intensity of the photoionizing radiation seen by atoms is determined by means of averaging the intensity distribution of the photoionizing beam over the spatial distribution of trapped atoms. We use the photoionizing laser beam with large waist to reduce a possible misalignment between the photoionizing beam and the MOT density distribution. The excited state fraction is also accurately measured under our MOT conditions. The near-threshold photoionization cross-section of lithium-7 2P3/2 state at λPI = 349.846(1) nm is found to be equal to σ = 13.7(1.4) Mb, with better accuracy in comparison with the previous measurements. We study the variation of the photoionization cross section on the polarization of the ionizing beam. Further experiments are suggested.

A data-driven framework is presented for building magneto-elastic machine-learning interatomic potentials (ML-IAPs) for large-scale spin-lattice dynamics simulations. The magneto-elastic ML-IAPs are constructed by coupling a collective atomic spin model with an ML-IAP. Together they represent a potential energy surface from which the mechanical forces on the atoms and the precession dynamics of the atomic spins are computed. Both the atomic spin model and the ML-IAP are parametrized on data from first-principles calculations. We demonstrate the efficacy of our data-driven framework across magneto-structural phase transitions by generating a magneto-elastic ML-IAP for α-iron. The combined potential energy surface yields excellent agreement with first-principles magneto-elastic calculations and quantitative predictions of diverse materials properties including bulk modulus, magnetization, and specific heat across the ferromagnetic–paramagnetic phase transition.

Characteristic features of polariton dispersion laws are studied for four-level atoms interacting with three pulses of coherent laser radiation with frequencies that are in resonance with optically allowed one-photon transitions 1 $$\leftrightarrows$$ 2, 2 $$\leftrightarrows$$ 3, and 3 $$\leftrightarrows$$ 4 with regard to two-photon transitions 1 $$\leftrightarrows$$ 3 and 2 $$\leftrightarrows$$ 4, as well as a direct three-photon transition 1 $$\leftrightarrows$$ 4. The approximation of a given photon density of three pulses is used. It is shown that the dispersion law consists of four branches the position and shape of which are specified by the Rabi frequencies of the above transitions and the photon densities of the three pulses. The direct consideration of all six optical transitions leads to the dependence of the dispersion law of atomic polaritons on quantum parameters—the phase differences between the Rabi frequencies of the transitions under consideration. Parameter values are found for which the branches of the dispersion law may intersect.

In this paper, we discuss the search for the Fulde–Ferrell–Larkin–Ovchinnikov superfluid phase in an ultracold gas of Fermi atoms. A possible obstacle to obtaining this phase in known experiments is, first of all, the separation of the gas into a spin-balanced phase and a completely polarized phase. This phase separation is caused by confinement in an external parabolic potential. A second possible obstacle is the insufficiently low temperature-to-Fermi energy ratio. Trapping the gas in a large-scale optical-dipole trap with a flat potential inside will avoid phase separation. Moreover, the trap will allow an increase in the number of atoms, which, in turn, can lead to a decrease in the temperature relative to the Fermi energy. The results of a primary experiment on loading atoms into a similar trap from a magneto-optical trap are presented.

Purpose: This work aims at investigating the zinc atoms in the triplet preionization – Rydberg states. The energy levels of atoms having two electrons outside the closed shell were studied mainly by the optical spectroscopy methods. However, just using the microwave spectroscopy to measure the frequency of transitions between the two Rydberg states allows to increase the accuracy of measurements in two or more orders of magnitude. Disign/methodology/approach:A line of three dye lasers is used to excite the zinc atoms into the triplet Rydberg states with a predetermined set of quantum numbers. The radiation of the first two of them is transformed into the second harmonic in nonlinear crystals. Dye lasers are excited by the radiation of the second harmonic of one YAG: ND3+ laser. All three radiations are reduced to the zone of interaction with the laser and the microwave radiation, which is located between the plates of the ionization cell, where the pulsed electric field is created. The excited Rydberg atoms are recorded with the field ionization procedure. The beam of neutral atoms is created by an effusion cell under the vacuum conditions, the residual pressure does not exceed 10-5 mm Hg. A pulsed electric field of some certain intensity results inionization of atoms excited by microwave radiation and in acceleration of electrons, which have appeared in the direction of the secondary electron multiplier, though being insufficient for ionization of atoms excited only by the laser radiation and which are initial for interaction with microwaves. By scanning the microwave radiation frequency with the given step and measuring the signal intensity of the secondary electron multiplier, the excitation spectrum of the atoms under study can be obtained. Findings: Using the created laser-microwave spectrometer, the frequencies of the F→D, F→F and F→G transitions between the triplet Rydberg states of zinc atoms were measured. From the analysis made of the transition frequencies, the quantum defect decomposition constants were obtained by the Ritz formula for the D, F, and G states of zinc atoms. Conclusions: The frequencies of the F→D, F→F and F→G transitions between the triplet Rydberg states of zinc atoms were measured that allowed obtaining the quantum defect decomposition constants according to the Ritz formula for the D, F and G states of zinc atoms, that in turn had allowed to calculate the energy of these terms and the transition frequencies at least in two orders of magnitude more accurately as against the similar measurements made by the optical spectroscopy. Key words: zinc atom, triplet states of atoms, Rydberg states, laser excitation, microwave radiation

This paper covers calculations of the activation energy of surface diffusion of ad-atoms on the substrate surface from the point of view of thermal oscillations of substrate atoms and ad-atoms. The main characteristic of oscillations of atoms and geometric mean frequency was calculated based on statistical approximation of the Debye model using the reference values of entropy and heat capacity of metals. The basic principle of the model of activation energy calculation presented in the paper is the formation of potential wells and barriers during oscillations of atoms localized in the sites of the lattice. Oscillations of atoms were considered in the framework of quasiclassical quantum approximation as the oscillations of harmonic oscillators in the potential parabolic wells. Dimensions of the negative part of values of the potential well energy were determined by the amplitude of thermal oscillations of atoms. Positive values constituted a significant part of the potential well energy values. Barriers were formed owing to interaction of positive values of the energy of parabolic wells of adjacent atoms. Therefore, in order to make the ad-atom jump, it is necessary to get out of the potential well having the negative values, and to overcome the potential barrier. The energy required for the ad-atom jump on the substrate surface was the activation energy of surface diffusion. The results obtained in this paper agree satisfactorily with the results of another method, which is based on determining the energy of ad-atom binding with the substrate atoms.

We examine the coherent dynamics of cold atoms in a three-dimensional (3D) optical lattice (OL) without interference between counter-propagating laser beams. The dynamics is treated in the semiclassical approximation taking into account a coupling between the atom internal and external degrees of freedom. This coupling has been shown before to lead to either regular or chaotic motion for a single two-level atom in dependence on the values of control parameters, the detuning between the atomic transition and laser frequencies, and the atom recoil frequency. In this paper, we carry out numerical experiments on spreading of clouds with a large number of cold noninteracting atoms at different values of the detuning allowing one to compare the evolution of atomic clouds in regular and chaotic regimes of motion. We show that the distributions of atoms differ in those regimes providing a way to control atomic transport by varying the detuning. We propose experimental measurements able to distinguish between the regular and chaotic regimes of atom motion and to observe a signature of chaos with real cold atoms in 3D OLs.

We present calculations of excitation energies, emitted photon wavelengths during the transition from upper level to lower level, transitions rates and other transition parameters for lowest 200 fine structure levels of Fe-like Xe, Cs and Ba ions by using multi-configuration Dirac–Fock (MCDF) technique. The significant contribution of the relativistic and quantum electrodynamic effects (QED) in addition to Breit corrections in energies of levels is observed and reported in this work. The calculated energies from both flexible atomic code (FAC) and General Purpose Atomic Structure Package (GRASP) are compared with the critically evaluated experimental NIST and other recent reported experimental and theoretical results. The computed data validate the experimentally available data. We have estimated the wavelengths of all soft X-ray (SXR) from the ground state in Fe-like isoelectronic sequence. Furthermore, sufficient new radiative data of Fe-like ions, which have not been published up to our knowledge, have been reported in present paper. Due to high abundance of iron (Z = 26) in cosmic environments, the present study can be beneficial in the field of modeling of fusion and astrophysical plasmas devices such as tokamaks, laser spectroscopy, electron beam ion trap (EBIT) cell biology and microscopic imaging.

The interaction between two modes quantized field and asymmetric two atoms represents one of the important quantum models to study the nonclassical quantized phenomena. The two modes multiphoton processes and interacting asymmetric two two-level atoms are introduced in the proposed quantum system. The time dependent solution of the proposed quantum system is computed analytically for asymmetric and symmetric cases. This analytical solution depends on the eigenvalues and the eigenvectors of the coefficient matrix of the Schrodinger equation. The nonclassical features of the proposed quantum system are evaluated as the entanglement and the atomic populations. The entanglement between atom and field is measured via the von Neumann entropy while the entanglement between two atoms is measured by the concurrence. These quantized features are analyzed for variety of the detuning parameter, the atom-atom coupling constant, and the numbers of two photon modes. The most important observations are that: If the numbers of two photon modes are identical, the von Neumann entropy is strong most of the time, the periodic time of the entropy and atomic populations is double comparing with other cases, and the concurrence is non-existent for asymmetric case. In the presence the detuning parameter and the atom-atom coupling constant, the von Neumann entropy increases with time while the amplitude of the concurrence decreases with time for symmetric case. The fluctuations of the von Neumann entropy for symmetric case are stable and uniform more than its for asymmetric case. The concurrence is irregular for asymmetric case. Furthermore, there are other quantized effects of the proposed model which are discussed for symmetric and asymmetric cases.

In this paper, the classical Bohr’s model of the hydrogen atom has been revisited. Two values of fundamental physical properties of an electron in the hydrogen atom has been identified. These physical properties ( & ) are constant in nature. The aim for the review was to contribute to the solution of disagreement between the Bohr’s wavelength ( ) and the Balmer’s experimental observation ( ) for the emission spectrum of hydrogen atom. There are two other constants and that were identified in the Bohr’s equation of the hydrogen atom. The four fundamental physical constants are intrinsic properties of an electron and can be applied to multi-electron system. They can also be obtained from Schrodinger’s equation for hydrogen atom at steady state. These constants may be subjected to scrutiny for their determination for better understanding. Also, since Bohr’s model of hydrogen atom is based on classical mechanics, this paper has provided an alternate method of solving simple problems in atomic physics under Bohr’s model to aid good mental picture of hydrogen atom to scientists.

In the present work a simple and lucid method of calculation of percentage ionization or degree of ionization is explained.

Fractional-spin errors are inherent in all current approximate density functionals, including Hartree-Fock theory, and their origin has been related to strong static correlation effects. The conventional way to encode fractional-spin calculations is to construct an ensemble density that scales between the high-spin and low-spin densities. In this article, we explore the variation of the Hartree-Fock fractional-spin (or ghost-interaction) error in one-electron systems using restricted and unrestricted ensemble densities, and the exact generalized Hartree-Fock representation. By considering the hydrogen atom and H$_2^+$ cation, we analyze how the unrestricted and generalized Hartree-Fock schemes minimize this error by localizing the electrons or rotating the spin coordinates. We also reveal a clear similarity between the Coulomb hole of He-like ions and the density depletion near the nucleus induced by the fractional-spin error in the unpolarized hydrogen atom. Finally, we analyze the effect of the fractional-spin error on the M{\o}ller-Plesset adiabatic connection, excited states, and functional- and density-driven errors., Comment: 12 pages, 9 figures

A discrepancy of 4σ (σ is the standard deviation) between the proton radii obtained by measuring transition frequencies in electron (H) and muonic (µH) hydrogen atoms has been actively discussed in the last decade. Theoretical and experimental efforts are focused on the test of this discrepancy and search for effects removing it. Recent measurements of the 2s–4p transition and the Lamb shift in the electron hydrogen atom approach the solution of the “proton radius puzzle.” The rms proton radius rp calculated from these experimental data is 0.8335(95) fm, which is in agreement within the indicated errors with a value of 0.84087(39) fm obtained from experiment with muon hydrogen. This agreement between the results has been achieved by including interference effects appearing in the processes of single-photon scattering on the hydrogen atom, whereas experiments on muonic hydrogen are insensitive to these effects. However, the charge radius of the proton cannot be calculated taking into account only single-photon transitions and measured frequencies corresponding to two-photon transitions should be taken into account. In this work, it has been shown that interference effects in the 2s–nd transitions in the hydrogen atom can make a significant contribution to the determination of the charge radius of the proton and Rydberg constant.

Dissipative Kerr solitons (DKS)s offer an integrated platform for broad spectrum coverage, which is suitable for the high sensitivity spectroscopy. However, the large linespacing of the soliton comb limits the spectroscopy detection resolution. We overcome this limitation by modulating the soliton comb lines through an external EOM with a tunable RF source. By locking the pump laser to a reference cavity, the linewidth of the pump laser was compressed from $1.13\:\mathrm{MHz}$ to $72\:\mathrm{kHz}$, leading to the silimar linewidth of comb lines and showing a frequency resolution of hundreds of $kHz$. Based on the scanned microcomb, we measured the absorption spectra of a gas cell and the high-Q optical modes in the microcavity, with a fast scanning speed of $\mathrm{16\,\,\mathrm{GHz/\mu s}}$. The scanning comb allows the spectroscopy measurement to cover the whole comb mode spectrum over THz bandwidth. Our setup holds great potential for simple, robust spectroscopy measurement.

The first solar radio line attributed to atomic hydrogen was theoretically grounded by J.P. Wild in 1952. Its Zeeman profile was calculated and reliably established in the radiation from quiet Sun regions and activity features over sunspots in 2018 using observations with the RATAN-600 radio telescope, leading to the determination of several parameters of the line emitting regions and the estimation of magnetic fields in the solar atmosphere. In this paper, we calculate the Zeeman profile for two more hydrogen radio lines and show that they can be observed in activity features over sunspots.

The interaction of an ultrashort (~10 fs) laser pulse with a relativistic intensity (≳1018 W/cm2) with a cluster medium characterized by a random distribution of large, submicron clusters of heavy atoms has been studied. Matching conditions for the parameters of the cluster medium and the laser pulse have been determined under which the yield of hot electrons is maximal at a given laser energy. The stochastic dynamics of laser-heated electrons in the Coulomb fields of clusters after the passage of the pulse determines the formation of a plateau with signatures of quasimonochromaticity in the energy spectrum of electrons in the ponderomotive energy range, which is important for the generation of the secondary electromagnetic radiation.

A new technique to measure phase noise properties of highly coherent lasers based on delayed self-heterodyne interferometer (DSHI) is suggested where the Allan variance of the beat note frequency is obtained via digital signal processing and then used to determine laser linewidth and phase noise properties. This method is capable of determining both white frequency noise and flicker-noise contributions and has been used to characterize various types of lasers. A simple numerical model generalizing previous analytical results has been developed and verified. The corresponding requirements imposed on the DSHI optical delay are consistent with numerical modeling results. The measurement results are in agreement with our previous experiments based on direct heterodyning of the same lasers. The technique is particularly suitable for real-time monitoring of the laser phase noise over long periods of time, which is useful for testing and engineering of highly coherent lasers.