Acoustic radiation from a drop due to its nonlinear vibrations

It is shown that the intensity of acoustic radiation from a vibrating drop depends mainly on the monopole and dipole components appearing only in the second order of smallness in vibration amplitude. The intensity of the quadrupole acoustic radiation generated by the vibration fundamental mode in the first order of smallness in amplitude turns out to be much weaker. This is associated with the fact that, if the acoustic wavelength is much larger than the drop characteristic size, their ratio becomes a governing small parameter, being lesser than the ratio of the drop vibration amplitude to the drop linear size. Analytical estimates of the amplitudes of monopole, dipole, and quadrupole components of the velocity field associated with the acoustic field of the drop.     

Relativistic corrections to the Lagrangian for interacting charged particles

We give the Lagrangian of a system of moving charged particles up to the fourth approximation in 1/c neglecting dipole radiation of the system. In this case the appearance of the electromagnetic waves (quadrupole radiation) by moving charges occurs in the fifth approximation in 1/c.     

A numerical analytic method for electromagnetic radiation accompanying with fracture of rocks

This paper studies Rabinovitch’s compression experiments on granite and chalk and proposes an oscillating dipole model to analyse and simulate the electromagnetic radiation phenomenon caused by fracture of rocks. Our model assumes that the electromagnetic radiation pulses are initiated by vibrations of the charged rock grains on the tips of the crack. The vibrations of the rock grains are stimulated by the pulses of the cracks. Our simulations show comparable results with Rabinovitch’s compression experiments. From the simulation results, it verifies an assumption that the crack width is inversely proportional to the circular frequency electromagnetic radiation, which is presented by Rabinovitch et al. The simulation results also imply that, by using our oscillating dipole model together with Rabinovitch’s two equations about the crack length and crack width, we can quantitatively analyse and simulate the electromagnetic radiation phenomenon, which is induced from the fracture of the rocks.     

Electromagnetic radiation due to nonlinear oscillations of a charged drop

The nonlinear oscillations of a spherical charged drop are asymptotically analyzed under the conditions of a multimode initial deformation of its equilibrium shape. It is found that if the spectrum of initially excited modes contains two adjacent modes, the translation mode of oscillations is excited among others. In this case, the center of the drop’s charge oscillates about the equilibrium position, generating a dipole electromagnetic radiation. It is shown that the intensity of this radiation is many orders of magnitude higher than the intensity of the drop’s radiation, which arises in calculations of the first order of smallness and is related to the drop’s charged surface oscillations.     

Cosmological effects of superconducting strings

Superconducting cosmic strings are a plausible consequence of symmetry breaking in grand unified gauge theories. The luminosity in electromagnetic radiation of an oscillating current-carrying loop may substantially exceed the luminosity in gravitational radiation. In the typical case considered, the energy released electromagnetically is 10⁴⁹ erg s⁻¹, or 10⁶⁶ erg in toto. Several consequences follow from this, the most interesting of which is the possibility that such loops may heat their surroundings, generating large, dense spherical shells of gas. Galaxies forming on these gravitationally unstable shells at moderate redshift will be seen at the present epoch to lie on bubbles having radii in the range 10–20h⁻¹ Mpc if the initial ratio of luminosity in electromagnetic waves to that in gravitational wavess is > 10⁻³ for mass/length 10²² g cm⁻¹. The required primordial energy density in magnetic fields is > 3 × 10⁻⁹ of the radiation energy density, if the charge carriers are bosons or superheavy fermions. Since these shells fill up space, the galaxies will have a distribution similar to that found in a recent survey of the northern sky. When the current saturates, a loop will emit particles copiously, and may be seen as an X-ray source at z ∼ 10–50. Such loops may also contribute significantly to the hard X-ray and γ-ray backgrounds and to 10²⁰ eV cosmic rays.     

磁偶极和电四极在磁各向异性介质中的辐射功率

在经典电动力学的框架下,研究了磁各向异性介质中的电磁辐射问题,得到了磁偶极和电四极在磁各向异性介质中的辐射功率表达式.进一步地,通过把各向同性介质中的μrii代入所得辐射功率表达式,得到了与文献相符合的结果,验证了所得结果的正确性.研究结果表明磁偶极和电四极在磁各向异性介质中的辐射功率大小与磁各向异性介质的μrii大小有关,对判断磁偶极和电四极在磁各向异性介质中的辐射效果有较大的帮助.     

Magnetooptical compression of atomic beams

We consider the propagation of an atomic beam in a quadrupole magnetic field under transverse irradiation by a cooling laser field. The cooling laser field was chosen in the form of a two-dimensional σ⁺-σ^? configuration. We show that the sub-Doppler resonance in the radiation force can be used to reduce the diameter of the atomic beam to a value on the order of 10 mm. We establish that the simultaneous transverse cooling and compression of the atomic beam allow its phase density to be increased to values of the order of 10^?4–10^?3. The dipole interaction of an atom with the cooling and compressing laser field in a quadrupole magnetic field is analyzed in terms of a simple (3 + 5)-level model atom.

     

Isomer ratio measurements for the reaction 29Si(18O,p2n)44m, 44gSc

Isomer ratios for the reaction ²⁹Si(¹⁸O, p2n)^44gSc, ^44gSc have been deduced from activity measurements for projectile energies between 30 and 99 MeV. Statistical model calculations show that the isomer ratio dependence on projectile energy up to about 80 MeV can be adequately described by assuming a fixed ratio of quadrupole to dipole γ-ray strengths. Such a ratio of E2/E1 strengths agrees with corresponding values deduced from the literature. The values of the γ-ray strength ratios needed to fit the experimental isomer ratios are extremely sensitive to the relative amounts of quadrupole γ-ray admixture and to the presence of discrete levels other than those which conform to the yrast line.     

Quadrupole electromagnetic radiation of an oscillating charged droplet

Analytical calculations using the first order of smallness with respect to dimensionless amplitude of oscillations show that the intensity of electromagnetic radiation of a charged droplet is determined by time-dependent quadrupole moment.     

Gravitational collapse with charge and small asymmetries. II. Interacting electromagnetic and gravitational perturbations

Paper I analyzed the evolution of nonspherical scalar-field perturbations of an electrically charged, collapsing star; this paper treats coupled electromagnetic and gravitational perturbations. It employs the results of recent detailed work in which coupled perturbations were studied in a gauge-invariant manner by using the Hamiltonian (Moncrief s) approach and the Newman-Penrose formalism, and the relations between the fundamental quantities of these two methods were obtained.It is shown that scalar-field perturbations are a prototype for coupled perturbations. The collapse produces a Reissner-Nordström black hole, and the perturbations are radiated away completely. Alll-pole parts of the perturbations of the metric and the electromagnetic field decay according to power laws; in the extreme case (e ² =M ²), the interaction causes the quadrupole perturbations to die out more slowly than the dipole perturbations.     

Radiative quenching and excitation of metastable states upon differential scattering of atoms: II. The He(1<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>–2<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>)-Ne molecule

The differential cross sections of radiative-collisional quenching (absorption) of a metastable state of a colliding atom are calculated for the first time. As a particular example, the reaction of quenching (excitation) of the metastable state He(2¹S) in collisions with Ne atoms in the ground state is considered. The calculations are performed for the thermal collisional energy E = 10^?3 au for a wide range of radiation frequencies, including both wings and the center of the line of a forbidden atomic transition, and are based on the uniform quasi-classical approximation, which generalizes the Franck-Condon approximation to the case of an exponential dependence of the transition dipole moment on the internuclear distance, as well as to the case of nonintersecting terms. The calculated differential cross sections have an oscillating structure, which, for the blue wing of the forbidden spectral line, is interpreted as Stückelberg oscillations. At a radiation frequency close to the frequency of the forbidden atomic transition, a sharp maximum in the differential cross section—the giant glory effect—is observed in the range of small scattering angles. This effect is shown to occur as a result of superimposition of the rainbowlike feature of the differential cross section on the glory feature.     

Monte Carlo simulation of the three-dimensional XY model with bilinear–biquadratic exchange interaction

The three-dimensional XY model with bilinear–biquadratic exchange interactions J and J′, respectively, has been studied by Monte Carlo simulations. From the detailed analysis of the thermal variation of various physical quantities, as well as the order parameter and energy histogram analysis, the phase diagram including two different ordered phases has been determined. There is a single phase boundary from a paramagnetic to a dipole–quadrupole ordered phase, which is of second order in a high J/J′ ratio region, changing to a first-order one for 0.35⩽J/J′⩽0.5. Below J/J′=0.35 there are two separate transitions: the first one to the quadrupole long-range order (QLRO) phase at higher temperatures, followed by another one to the dipole–quadrupole long-range order (DLRO) phase at lower temperatures. The finite-size scaling analysis yields values of the critical exponents for both the DLRO and QLRO transitions close to the values for the conventional XY model which includes no biquadratic exchange.     

Electromagnetic decay of the giant quadrupole resonances: (II). Nuclear structure aspects

We analyze experiments on the electromagnetic decay of the GQR from the point of view of the microscopic theory of the nuclear structure. The calculations are made systematically in the lowest contributing order of perturbation theory within the NFT formalism. Care is taken in order to prevent spurious mixing of the isoscalar and isovector parts of dipole operators. As in previous theoretical calculations, the results are consistent with the experimental limit of the ratio between the transition populating the 2.62 MeV 3⁻ state and the g.s. However they fail to reproduce the strong dipole transition to the 4.97 MeV 3⁻ state.     

Effects of high-frequency and high-voltage pulsed electric field parameters on water chain formation

Separation methods utilizing high-frequency and high-voltage pulsed DC electric fields have been used extensively in the oil and petroleum industries, where the occurrence of water-in-oil dispersions is highly unwelcome because of physical constraints and the high maintenance costs required to treat these dispersions. This paper reports the results of studies of the effects of applied electric field parameters, including electric field strength, frequency, and duty ratio, on water chain formation in water-in-oil emulsions. The investigations were performed in a rectangular Perspex^® cell. The results of the studies show that dipole–dipole forces dominate the process of water chain formation. At low electric field strength, frequency, or duty ratio, dipole–dipole forces are negligible; therefore, the process of water chain formation and aqueous drop coalescence are inconspicuous. However, at high electric field strength, frequency, or duty ratio, significant dipole–dipole forces give rise to water chain formation and aqueous drop coalescence. At extremely high electric field strength, frequency, or duty ratio, aqueous drops are excessively polarized and disintegrate, inhibiting the processes of water chain formation and aqueous drop coalescence. The optimum electric field parameters for separation of water-in-oil dispersions are as follows: electric field strength, 3.80 kV cm⁻¹; frequency, 4.0 kHz; and duty ratio, 0.65.     

Four-body calculation of <Superscript>12</Superscript>C(<Emphasis Type="Italic">α, γ</Emphasis>)<Superscript>16</Superscript>O radiative capture reaction at stellar energies

On the basis of the four-alphamodel, the ¹²C(α, γ)¹⁶Oradiative capture process is investigated by using the four-body Faddeev–Yakubovsky equations as well as the two- and three-body electromagnetic currents. The present calculation is an application of our current conservation realistic potentials method for the ¹²C(α, γ)¹⁶Oradiative capture process. This work clears the way formore refinedmodels of radiative capture based on two- and three-body realistic potentials and current conservation. The calculation is carried out by considering the ⁴He + ¹²C (1 + 3) and the ⁸Be + ⁸Be (2 + 2) subamplitudes, respectively. Radiative capture ¹²C(α, γ)¹⁶Oreaction is one of the most important reactions in nuclear astrophysics. For this reaction, the electric dipole transitions between states with the same isospin are forbidden in the first order. Because the state 1⁺ and 0⁺ ground state nuclei ¹⁶O have zero isospin, thus the electric dipole radiations are not at the first order between two levels and electric dipole radiation will be the second order and electric dipole radiation is the same order as the electric quadrupole radiation. Therefore, we must consider the effects of both radiations. In comparison with other theoretical methods and available experimental data, good agreement is achieved for the E₁ and E₂ contribution to the cross section and the astrophysical S factor for this process.     

Nonlinear vibrations of a charged drop due to the initial excitation of neighboring modes

The asymptotic analysis of the nonlinear vibrations of a charged drop that are induced by a multi-mode initial deformation of its equilibrium shape is performed. It is shown that when two, three, or several neighboring modes are present in the initial deformation spectrum, the mode with the number one (translational mode) appears in the second-order mode spectrum. The excitation of the translational mode follows from the requirement of center-of-mass immobility and causes the dipole components (which are absent in the linear analysis) to appear in the spectra of the acoustic and electromagnetic radiation of the charged drop.     

Status of deceleration and laser spectroscopy of highly charged ions at HITRAP

Heavy few-electron ions are relatively simple systems in terms of electron structure and offer unique opportunities to conduct experiments under extremely large electromagnetic fields that exist around their nuclei. However, the preparation of highly charged ions (HCI) has remained the major challenge for experiments. As an extension of the existing GSI accelerator facility, the HITRAP facility was conceived as a multi-stage decelerator for HCI produced at high velocity. It is designed to prepare bunches of around 10⁵ HCI and to deliver them at low energies to various experiments. One of these experiments is SpecTrap, aiming for laser spectroscopy of trapped, cold HCI. We present the latest results on deceleration of ions in a radio-frequency quadrupole, synchrotron cooling of electrons in a trap as a preparation step for the prospective electron cooling of the HCI decelerated in HITRAP, as well as laser cooling of singly charged Mg ions for sympathetic cooling of HCI in SpecTrap.     

Coulomb dissociation of 11Li

We use a semiclassical treatment of the coupled-channels problem to study the Coulomb dissociation of ¹¹Li projectiles on a heavy target. The comparison of our predictions with the data show good agreement for the energy spectrum and qualitative agreement for the velocity distribution. The effect of going beyond the dipole term of the electromagnetic coupling is studied and other improvements over the calculations presented in a previous work are also considered.