Quadrupole Emission Research Articles

THE STUDY OF ELECTRIC QUADRUPOLE TRANSITION (E2) IN 58Ce AND 60Nd NUCLEI

Transition strengths 2w.u. M(E2) for gamma transition from first excited 21+statesto the ground states that produced by pure electric quadrupole emission in even –even nuclei of 58Ce and 60Nd have been calculated as a function of neutron number(N). The life times for 21+ excited states together with the intensities of γ0- transitionsmeasurements are used in calculations. The results thus obtained have shown that;the nuclei with magic neutron number such as 58Ce140 and 60Nd142 have minimumvalue for 2w.u. M(E2) . The reduced transition probabilities B(E2) are alsocalculated and compared with the experimental data and other theoretical models.PACS:- 27.60-j, 23.20-g, 23.20.Ck, 23.20.Gq

Comparison of neural network architectures for feature extraction from binary black hole merger waveforms

We evaluate several neural-network architectures, both convolutional and recurrent, for gravitational-wave time-series feature extraction by performing point parameter estimation on noisy waveforms from binary-black-hole mergers. We build datasets of 100 000 elements for each of four different waveform models (or approximants) in order to test how approximant choice affects feature extraction. Our choices include SEOBNRv4P and IMRPhenomPv3, which contain only the dominant quadrupole emission mode, alongside IMRPhenomPv3HM and NRHybSur3dq8, which also account for high-order modes. Each dataset element is injected into detector noise corresponding to the third observing run of the LIGO-Virgo-KAGRA (LVK) collaboration. We identify the temporal convolutional network architecture as the overall best performer in terms of training and validation losses and absence of overfitting to data. Comparison of results between datasets shows that the choice of waveform approximant for the creation of a dataset conditions the feature extraction ability of a trained network. Hence, care should be taken when building a dataset for the training of neural networks, as certain approximants may result in better network convergence of evaluation metrics. However, this performance does not necessarily translate to data which is more faithful to numerical relativity simulations. We also apply this network on actual signals from LVK runs, finding that its feature-extracting performance can be effective on real data.

Silicon cuboid nanoantenna with simultaneous large Purcell factor for electric dipole, magnetic dipole and electric quadrupole emission

The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter. Here, we propose a silicon dielectric cuboid nanoantenna for simultaneously enhancing electric dipole (ED), magnetic dipole (MD) and electric quadrupole (EQ) emission. We study the scattering cross section, polarization charge distribution, and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna, from which we have identified simultaneous existence of ED, MD and EQ resonance modes in this nanoantenna. We have calculated the Purcell factor of ED, MD and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within the nanoantenna, respectively. We find that the resonances wavelengths of the Purcell factor spectrum are matching with the resonance modes in the nanoantenna. Moreover, the maximum Purcell factor of these ED, MD and EQ emitters is 18, 150 and 118 respectively, occurring at the resonance wavelength of 475, 750, and 562 nm, respectively, all within the visible range. The polarization charge distribution features allow us to clarify the excitation and radiation of these resonance modes as the physical origin of large Purcell factor simultaneously occurring in this silicon cuboid nanoantenna. Our theoretical results might help to deeply explore and design the dielectric nanoantenna as an ideal candidate to enhance ED, MD and EQ emission simultaneously with very small loss in the visible range, which is superior than the more popular scheme of plasmonic nanoantenna.

Enhancement of and interference among higher order multipole transitions in molecules near a plasmonic nanoantenna

Spontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna. This impact is usually evaluated under assumption that each molecular transition is dominated only by one multipolar channel, commonly the electric dipole. In this article, we go beyond the electric dipole approximation and take light-matter coupling through higher-order multipoles into account. We investigate a strong enhancement of the magnetic dipole and electric quadrupole emission channels of a molecule adjacent to a plasmonic nanoantenna. Additionally, we introduce a framework to study interference effects between various transition channels in molecules by rigorous quantum-chemical calculations of their multipolar moments and a consecutive investigation of the transition rate upon coupling to a nanoantenna. We predict interference effects between these transition channels, which allow in principle for a full suppression of radiation by exploiting destructive interference, waiving limitations imposed on the emitter’s coherence time by spontaneous emission.

Gravitational waveforms and radiation powers of the triple system PSR J0337+1715 in modified theories of gravity

In this paper, we study the gravitational waveforms, polarizations and radiation powers of the first relativistic triple systems PSR J0337 + 1715, observed in 2014, by using the post-Newtonian approximations to their lowest order. Although they cannot be observed either by current or next generation of the detectors, they do provide useful information to test different theories of gravity. In particular, we carry out the studies in three different theories, general relativity (GR), Brans-Dicke (BD) gravity, and Einstein-aether ($\ae$) theory. The tensor modes $h_{+}$ and $h_{\times}$ exist in all three theories and have almost equal amplitudes. Their frequencies are all peaked at two locations, $ f^{(+, \times)}_1 \simeq 0.0686656 \mu$Hz and $ f^{(+, \times)}_2 \simeq 14.2138 \mu$Hz, which are about twice of the outer and inner orbital frequencies of the triple system, as predicted in GR. In $\ae$-theory, all the six polarization modes are different from zero, but the breathing $h_b$ and longitudinal $h_L$ modes are not independent and also peaked at two frequencies, but at the frequencies, $ f^{(b, L, \ae)}_{1} \simeq 0.0457771 \mu$Hz and $f^{(b, L, \ae)}_{ 2} \simeq 7.09545 \mu$Hz. A similar phenomenon is also observed in BD gravity, in which only the three modes $h_{+},\; h_{\times}$ and $h_{b}$ exit. We also study the radiation powers, and find that the quadrupole emission in each of the three theories has almost the same amplitude, but the dipole emission can be as big as the quadrupole emission in $\ae$-theory. This can provide a very promising window to obtain severe constraints on $\ae$-theory by the multi-band gravitational wave astronomy.

How to search for gravitational waves from r -modes of known pulsars

Searches for continuous gravitational waves from known pulsars so far have been targeted at or near the spin frequency or double the spin frequency of each pulsar, appropriate for mass quadrupole emission. But some neutron stars might radiate strongly through current quadrupoles via $r$-modes, which oscillate at about four thirds the spin frequency. We show for the first time how to construct searches over appropriate ranges of frequencies and spin-down parameters to target $r$-modes from known pulsars. We estimate computational costs and sensitivities of realistic $r$-mode searches using the coherent $\mathcal{F}$-statistic, and find that feasible searches for known pulsars can beat spin-down limits on gravitational wave emission even with existing LIGO and Virgo data.

Extended calculations for energies and EUV transition data of W LIII

Energy spectra of the 3d4, 3d34s, 3d34p, and 3d34d configurations of W LIII are calculated using the ab initio multi-configuration Dirac-Fock method. The correlations within the n = 9 complex, n being the principal quantum number of the outermost electron are accounted for in a systematic way and the Breit interaction and quantum electrodynamics effect are evaluated. Wavelengths, oscillator strengths, electric dipole, electric quadrupole, magnetic dipole, and magnetic quadrupole emission transition rates regarding these levels are obtained. The Flexible Atomic Code (FAC) calculations are further performed to support these data. Results are compared with other available theory reported in the literature as well as the recommended experimental data listed in the Atomic Spectra Database (ASD) of the National Institute of Standards and Technology (NIST) online database. Satisfactory agreement is found between them. In light of these findings, the present complete and consistent results can aid line identifications in extreme ultraviolet (EUV) spectra and should be beneficial in fusion plasma research.

X-Ray Quadrupole Emission in the Scattering of Two Photons by a Multicharged Atomic Ion

Pronounced spectrally extended quadrupole X-ray emission has been theoretically predicted in resonant inelastic scattering of two photons near the ionization threshold energy of the 1s shell of a free multielectron atom. The observed double differential scattering cross section is estimated quantitatively. The results predicted for the Ar8+ ion possibly concern the problem of identification of X-ray emission spectra near 3.5 keV from galaxies and clusters of galaxies.

Effect of Quadrupole Emission in Scattering of Two Photons by an Atom

A pronounced quadrupole emission effect is theoretically predicted in terms of the contact interaction operator in resonant inelastic scattering of two X-ray photons near the ionization threshold energy of the 1s shell of a free multielectron atom. The observed double differential scattering cross section is estimated quantitatively.

Parametric Calculations of Radiative Decay Rates for Magnetic Dipole and Electric Quadrupole Transitions in Tm IV, Yb V, and Er IV

Semi-empirical transition probabilities for magnetic dipole (M1) and electric quadrupole (E2) emission lines have been derived from parametric studies of experimental energy levels in Tm3+ (Tm IV), Yb4+ (Yb V), and Er3+ (Er IV), using Cowan codes. Results are compared with those existing from ab initio calculations or from more sophisticated semi-empirical calculations. Satisfactory agreements show that simple parametric calculations can provide good predictions on line intensities, provided that experimental levels are available, allowing reliable fits of energy parameters.

About gravitational-wave generation by a three-body system

We highlight some subtleties that affect naive implementations of quadrupolar and octupolar gravitational waveforms from numerically-integrated trajectories of three-body systems. Some of those subtleties arise from the requirement that the source be contained in its ‘coordinate near zone’ when applying the standard PN formulae for gravitational-wave emission, and from the need to use the non-linear Einstein equations to correctly derive the quadrupole emission formula. We show that some of these subtleties were occasionally overlooked in the literature, with consequences for published results. We also provide prescriptions that lead to correct and robust predictions for the waveforms computed from numerically-integrated orbits.

Some comments on the electrodynamics of binary pulsars

We consider the electrodynamics of in-spiraling binary pulsars, showing that there are two distinct ways in which they may emit radiation. On the one hand, even if the pulsars do not rotate, we show that in vacuo orbital rotation generates magnetic quadrupole emission, which, in the late stages of the binary evolution becomes nearly as effective as magnetic dipole emission by a millisecond pulsar. On the other hand, we show that interactions of the two magnetic fields generate powerful induction electric fields, which cannot be screened by a suitable distribution of charges and currents like they are in isolated pulsars. We compute approximate electromotive forces for this case.

Mid-infrared spectroscopy of Uranus from the Spitzer Infrared Spectrometer: 1. Determination of the mean temperature structure of the upper troposphere and stratosphere

On 2007 December 16–17, spectra were acquired of the disk of Uranus by the Spitzer Infrared Spectrometer (IRS), ten days after the planet’s equinox, when its equator was close to the sub-Earth point. This spectrum provides the highest-resolution broad-band spectrum ever obtained for Uranus from space, allowing a determination of the disk-averaged temperature and molecule composition to a greater degree of accuracy than ever before. The temperature profiles derived from the Voyager radio occultation experiment by Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92, 14987–15001) and revisions suggested by Sromovsky et al. (Sromovsky, L.A., Fry, P.A., Kim, J.H. [2011]. Icarus 215, 292–312) that match these data best are those that assume a high abundance of methane in the deep atmosphere. However, none of these model profiles provides a satisfactory fit over the full spectral range sampled. This result could be the result of spatial differences between global and low-latitudinal regions, changes in time, missing continuum opacity sources such as stratospheric hazes or unknown tropospheric constituents, or undiagnosed systematic problems with either the Voyager radio-occultation or the Spitzer IRS data sets. The spectrum is compatible with the stratospheric temperatures derived from the Voyager ultraviolet occultations measurements by Herbert et al. (Herbert, F. et al. [1987]. J. Geophys. Res. 92, 15093–15109), but it is incompatible with the hot stratospheric temperatures derived from the same data by Stevens et al. (Stevens, M.H., Strobel, D.F., Herbert, F.H. [1993]. Icarus 101, 45–63). Thermospheric temperatures determined from the analysis of the observed H2 quadrupole emission features are colder than those derived by Herbert et al. at pressures less than ∼1μbar. Extrapolation of the nominal model spectrum to far-infrared through millimeter wavelengths shows that the spectrum arising solely from H2 collision-induced absorption is too warm to reproduce observations between wavelengths of 0.8 and 3.3mm. Adding an additional absorber such as H2S provides a reasonable match to the spectrum, although a unique identification of the responsible absorber is not yet possible with available data. An immediate practical use for the spectrum resulting from this model is to establish a high-precision continuum flux model for use as an absolute radiometric standard for future astronomical observations.

Intensity of electric quadrupole emission in oxygen investigated by means of a matrix formalism

A matrix formalism is introduced to study the intensity of electric quadrupole emission in oxygen. In fact, the total intensity of the electric quadrupole lines in the above emission is expressed in terms of matrices with full physical meaning whose main aspects are discussed.

The Einstein–Maxwell-particle system in the York canonical basis of ADM tetrad gravity. Part 2. The weak field approximation in the 3-orthogonal gauges and Hamiltonian post-minkowskian gravity: the N-body problem and gravitational waves with asymptotic background 1This paper is one of three companion papers published in the same issue of Can. J. Phys.

In this second paper we define a post-minkowskian (PM) weak field approximation leading to a linearization of the Hamilton equations of Arnowitt–Deser–Misner (ADM) tetrad gravity in the York canonical basis in a family of nonharmonic 3-orthogonal Schwinger time gauges. The York time 3K (the relativistic inertial gauge variable, not existing in newtonian gravity, parametrizing the family, and connected to the freedom in clock synchronization, i.e., to the definition of the the shape of the instantaneous 3-spaces) is set equal to an arbitrary numerical function. The matter are considered point particles, with a Grassmann regularization of self-energies, and the electromagnetic field in the radiation gauge: an ultraviolet cutoff allows a consistent linearization, which is shown to be the lowest order of a hamiltonian PM expansion. We solve the constraints and the Hamilton equations for the tidal variables and we find PM gravitational waves with asymptotic background (and the correct quadrupole emission formula) propagating on dynamically determined non-euclidean 3-spaces. The conserved ADM energy and the Grassmann regularization of self-energies imply the correct energy balance. A generalized transverse–traceless gauge can be identified and the main tools for the detection of gravitational waves are reproduced in these nonharmonic gauges. In conclusion, we get a PM solution for the gravitational field and we identify a class of PM Einstein space–times, which will be studied in more detail in a third paper together with the PM equations of motion for the particles and their post-newtonian expansion (but in the absence of the electromagnetic field). Finally we make a discussion on the gauge problem in general relativity to understand which type of experimental observations may lead to a preferred choice for the inertial gauge variable 3K in PM space–times. In the third paper we will show that this choice is connected with the problem of dark matter.

Gravitational-wave extraction from neutron-star oscillations: Comparing linear and nonlinear techniques

The main aim of this study is the comparison of gravitational waveforms obtained from numerical simulations which employ different numerical evolution approaches and different wave-extraction techniques. For this purpose, we evolve an oscillating, nonrotating, polytropic neutron-star model with two different approaches: a full nonlinear relativistic simulation (in three dimensions) and a linear simulation based on perturbation theory. The extraction of the gravitational-wave signal is performed via three methods: the gauge-invariant curvature-perturbation theory based on the Newman-Penrose scalar ${\ensuremath{\psi}}_{4}$; the gauge-invariant Regge-Wheeler-Zerilli-Moncrief metric-perturbation theory of a Schwarzschild space-time; some generalization of the quadrupole emission formula.

Sound generation by a vortex ring collision with a wall

Sound generation by a collision of a vortex ring with a free-slip/no-slip wall is investigated by using a direct numerical simulation. The three-dimensional, unsteady, compressible Navier–Stokes equations are solved by a finite difference method, not only for a near-vortical flow field but also for a far-acoustic field. By comparing free-slip and no-slip problems, we discuss the effects of the no-slip boundary condition at the wall surface on the near and far fields. In addition, a new three-dimensional expression to predict the far-field sound pressure is proposed based on the theory of vortex sound. Then, by using the new expression, we discuss the relation between the vortical phenomenon and the acoustic wave modes. For normal collision with a no-slip wall, a secondary vorticity layer is produced on the wall surface because of the no-slip condition, and then forms secondary and tertiary vortex rings. The mutual interaction between the primary and secondary/tertiary vortex rings induces a rebounding motion of the primary vortex ring. The sound pressure radiated by the collision has a quadrupolar nature, and its generation is closely related to the rebounding motion. For oblique collision with a no-slip wall, the secondary vortical structure consists of helical vortex lines. The variations in vorticity moment associated with the formation of the helical vortex lines affect the quadrupole emission. In this case, in addition to the quadrupole and octupole modes, the dipole mode is also observed which is not observed in the free-slip case. The new expression proposed shows that the generation of the dipole in the no-slip case is related to the wall shear stress and the velocity distribution.

On the existence of dipole satellites in the region of M2,3-L2,3non-dipole emission lines for transition elements

The reason of discrepancy between the experimental and the theoretical relative intensities of the 3p!2p electric quadrupole emission with respect to dipole 3s!2p emission for transition elements is investigated in relativistic conguration interaction approximation. The enhancement of theoretical intensity of quadrupole transitions by 4n6 times is obtained. It is shown that their relative intensity increases with the atomic number. In the single conguration approximation the dipole and the quadrupole transitions are separated in energy, but taking into account the conguration mixing their energy intervals extend and overlap. The dipole CI satellites with intensity exceeding the intensity of quadrupole transitions appear in their region, thus their separation becomes hardly possible.

Fine‐structure physical chemistry modeling of Uranus H2 X quadrupole emission

A new hydrogen physical chemistry model has been developed at the fine‐structure level for application to the giant outer planet thermospheres. The model is applied to Uranus because observations of dayglow H2 X 1Σg+ (v) quadrupole and H3+ vibration‐rotation emission made at NASA IRTF and UKIRT provide critical constraints for thermospheric modeling. The observed H3+ vibration‐rotation emission infers an H3+ dominant ionosphere, predicted only for non‐LTE H2 X (v : J). Excitation mechanisms explored are solar and non‐solar electron energy deposition. Non‐solar electron forcing is constrained by the EUV H2 Lyman and Werner band emission measured by Voyager UVS. Analysis indicates that non‐solar electrons are dominant in the energy budget required to predict the observed thermospheric temperature profile. The modeled H2 X quadrupole emission infers that an additional mechanism is required to excite the H2 X (v = 1) population. Non‐thermal H produced in dissociative excitation of H2 X is a primary candidate.

Excitation ofg-modes of solar-type stars by an orbiting companion

The possibility of exciting the g-modes of a solar-type star as a consequence of the gravitational interaction with a close companion (a planet or a brown dwarf) is studied by a perturbative approach. The amplitude of the emitted gravitational wave is computed and compared with the quadrupole emission of the system, showing that in some cases it can be considerably larger. The effects of radiation reaction are considered to evaluate the time scale of the emission process, and a Roche lobe analysis is used to establish the region where the companion can orbit without being disrupted by tidal interactions with the star.