Scattering spectra of dielectric ring: microwave experiments

In recent years, dielectric ring resonators (RRs) have become an essential part of integrated optical circuits. This determines the growing interest in the study of the fundamental electromagnetic properties of these objects, which is far from complete. In particular, in the literature it is difficult to find information about light scattering spectrum, which should demonstrate a strong resonance character when the probe wavelength is comparable to the geometric dimensions of the RR, taking into account its dielectric constant. In this work, we present the results of an experimental study of the electromagnetic properties of a dielectric RR in the microwave range of the spectrum. The results of numerical calculations of the scattering spectrum are also presented, which demonstrate excellent agreement with the experimental data. In addition to the expected resonance character of the spectrum, we report the effects of strong light confinement, which are associated with Fano resonances between the eigenmodes and the component of the electromagnetic field scattered by the ring.

Resonance refraction and neutrino oscillations

The refraction index and matter potential depend on neutrino energy and this dependence has a resonance character associated to the production of the mediator in the s−channel. For light mediators and light particles of medium (background) the resonance can be realized at energies accessible to laboratory experiments. We study properties of the energy dependence of the potential for different C-asymmetries of background. Interplay of the background potential and the vacuum term leads to (i) bump in the oscillation probability in the resonance region, (ii) dip related to the MSW resonance in the background, (iii) substantial deviation of the effective ∆m2 above the resonance from the low energy value, etc. We considered generation of mixing in the background. Interactions with background shifts the energy of usual MSW resonance and produces new MSW resonances. Searches of the background effects allow us to put bounds on new interactions of neutrinos and properties of the background. We show that explanation of the MiniBooNE excess, as the bump due to resonance refraction, is excluded.

The non-stationary delay of establishment nonlinear vibrations in the system of two connected oscillators. Part 3. Determinating equation.

This work is the continuation of investigation of non-stationary delay of establishment nonlinear vibrations in the system of two connected oscillators. The physical foundation of this task is the excitation of power hypersound in ferrite plate having magnetoelastic properties and also excitation of intensive electromagnetic vibrations in ferrite disc placed in electro-dynamic resonator. The foundation of this work is received in the first part of this work the simplified system of two connected differential second order equations having vibration character. As a main step of simplification of the task it is made the substitution of the vibration of second oscillator by auxiliary function having harmonic dependency from the time. In this case the dynamic potential acquired the character of periodic “jumps” in forward and backward directions. By this circumstance the introduced function was named as “jumping”. As a result of introduction of jumping function it was the replacement of two equations of initial system by only one “determination” equation which maintains the properties of the large-amplitude chaos and non-stationary delay. On the basis of determination equation it is investigated the development of vibrations and founded its derivative in the time and the parametrical portrait is constructed. It is shown that the development of vibrations feels large delay in time which value surpass the period of jumping function about some times. When the delay is over it is developed by the sudden jump the non-stationary vibrations having the amplitude which surpass the initial displacement more then three orders. The parametrical portrait has the form of horizontal eight which is typical for chaotic vibrations. The spectrum composition of large-amplitude chaos is investigated. It is shown that in the whole spectrum is predominated the line which is correspond to frequency of jumping function. When this function is removed it is remained only clean chaos. The width of spectrum of this chaos exceeds the frequency of jumping function on two orders. The influence of initial displacement on delay time is investigated. It is shown that the delay time is depended on the value of initial displacement in the frame of inverse proportion law. The influence of jumping function amplitude on the delay time is investigated. It is found the critical value of this amplitude. It is shown that in the lower level of critical value the large-amplitude chaos is absent. It is shown that when the amplitude of jumping function increases the delay time is decreases. But on the general smooth dependence it is displaced some sharp maxima which correspond to sharp increasing of delay time on the value about one order and more. As a possible explanation of this dependence character it is proposed the hypothesis about its resonance character. The influence of jumping function frequency on the delay time is investigated. It is shown that when this frequency is increased the delay time also increases right until its critical value. Above the level of critical value the large-amplitude chaos is absent. It is noted the analogy of this phenomenon with the excitation of electric vibration circuit by sinusoidal force. In this case on the low frequency the current in the circuit vibrates in the same phase with excitation force and after the overcoming the resonance frequency the vibrations becomes in opposite phase. On the received dependence it if found some narrow maxima which corroborate the hypothesis about its resonance character. It is found that the determination equation contains inertial and potential parts for the characteristics of which is introduced the inertial and potential parameters as a coefficients by second derivative and item of cubic nonlinearity. The influence of inertial parameter on the delay time is investigated. It is found the critical value of this parameter lower of which the large-amplitude chaos is absent. The influence of potential parameter on the delay time is investigated. It is found that the excitation of large-amplitude chaos is possible along unlimited range of this parameter without some critical value. The influence of phase displacement of jumping function in comparison with initial moment of excitation on the delay time is investigated. It is found very strong dependence which is differed by small and large delay times. The small value of delay time is characterized by absence of sharp maxima on the dependence of delay time from initial displacement. It is shown that in this case the dependence of delay time from of phase displacement has very wide maximum when the dependence of jumping function is negative. In this region the large-amplitude chaos is absent. It is found that by large delay times so as in region of sharp maxima on the dependence of delay time from initial displacement the influence of phase displacement of jumping function is sharp increased. It is proposed some comments about possible development of this work. As a general tasks it is mentioned the construction of model idea about duration of delay time, more detailed clarification of nature of critical character of some parameters and more detailed investigation of phase character of described phenomena.

Аномальные характеристики ионной эмиссии при разрыве полимеров

Measurements of the current-voltage characteristics of ion emission during the rupture of film samples of polyethylene terephthalate, polyimide, and polyphenylene ether in high vacuum have been carried out. Positive ions begin to be detected at a pulling potential of 100–200 V, and their number monotonically increases to saturation with increasing potential. Emission of negative ions is observed at a potential of << 200 V and in the range of 0–50 V has a resonance character, and the position of the resonance peaks is determined by the nature of the polymer. The discovered resonant nature of negative ion emission corresponds to the proposed physical mechanism of ion formation

Numerical Simulations of Instability in the Shell of a Supernova Remnant Expanding in a Weakly in Inhomogeneous Interstellar Medium

Astronomical observations show that the supernova remnants, even with a close to spherical shape, usually have multiscale ripple-like distortions. For example 15 bends on the shock front are clearly visible in the remnant 0509-67.5. The global instability of the flow is considered as one of the possible mechanisms for generating such structures. In the frame of linear analysis [26] was shown that this instability has a resonance character. It means that the perturbations with a certain wavelength number should grow faster, therefore ripples in the remnant shell will manifest itself predominantly in a certain range of scales. In this paper we present the results of numerical simulations of the nonlinear stage of this instability, caused by small perturbations in the external environment, depending on their scale and intensity. The unpertubed gas is supposed to has a power-law spartial dependence ρ0(r) ~ r-ω, where ω is a constant. The blast wave generated by a supernova expolosion is descibed by a Sedov type similarity solution. We have developed two-dimensional numerical model of adiabatic flow with a blast wave in a comoving frame of reference based on parallel code AstroChemHydro [1]. It was shown that, according to the predictions of linear analysis, perturbations in the external flow amplify behind the front of the shock wave, which leads to the development of convective instability and the development of turbulence. The results of numerical simulations demonstrated that in shell-type flows (for omega = 2,7 and gamma = 4/3) external disturbances along with the characteristic rearrangement of the shock front and turbulization of the flow behind it, cause the formation of radially elongated filaments with a vortex structure behind the shock, the number of which is determined by the harmonic number of the perturbation l.

GIANT M1 RESONANCE ON THE GROUND AND EXCITED STATES IN 2s1d-SHELL NUCLEI

The gamma decay of the resonance-like structures observed in the reaction of radiative capture of protons by the nuclei 22Ne, 26Mg, 30Si, 34,36S, and 38Ar in the region of excitation energies of 7…12 MeV was studied. The excitation functions of this reaction were measured. The resonance strengths in the energy range of the accelerated protons Ep = 1.0…3.0 MeV were determined. The obtained discrete distributions of the magnetic dipole γ-transitions on the ground and excited states for the nuclei of the 2s1d-shell have resonance character. Giant M1 resonance on the ground and excited states in the 23Na, 27Al, 31P, 35.37Cl, and 39K nuclei has been identified. The position of the M1 resonance on excited states coincides with that predicted by the Brink-Axel hypothesis for nuclei that are at the beginning of the subshell.

Резонансное поглощение электромагнитного излучения в монослое фосфорена

The absorption coefficient of the electromagnetic radiation in a phosphorene single layer placed in a magnetic field is found. A degenerate and nondegenerate electron gas is considered. The resonant dependences of the absorptance on the radiation frequency and applied magnetic field are found. Taking into account electron scattering at an ionized impurity leads to oscillation dependences of the absorption coefficient on the radiation frequency and external magnetic field. The resonance character of the absorption curve is shown. The conditions of resonances and position of resonance peaks are found.

Электроакустическое возбуждение спиновых волн и их детектирование за счет обратного спинового эффекта Холла

—In this paper, we present theoretical and experimental results on the excitation and detection of spin waves and spin currents in multifrequency bulk acoustic wave resonators containing iron–yttrium garnet (YIG) films in contact with the Pt film. Acoustically excited magnetic precession under the resonator conditions was established to produce spin pumping that also has a resonance character. A significant asymmetry in the frequency dependence of the voltage signal detected on the Pt film is revealed with respect to the frequency of the magnetoelastic resonance and is confirmed by theoretical calculations. Acoustic resonator spectroscopy in combination with the electric detection of magnetic dynamics using the inverse spin Hall effect is shown to be of interest for studying the dispersion of spin waves, as well as magnetic and magnetoelastic parameters of ferromagnetic films.

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance

A ‘sandwich'-structured TiO 2 NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO 2 nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy ‘antennas' to trap the local-field light near the TiO 2 NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO 2 NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO 2 NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices.