Cross-sectional Resonance Research Articles

Localised plasmons in sphere-like fullerenes and nanoparticles with conducting shells: Classical electrodynamic approach

Based on the classical electrodynamic approach, we consider localised plasmons in fullerenes and small particles with metal layers and shells. At low energies of the radiation quantum, models of fullerenes as conducting shells are used taking into account the contribution of only π electrons, and at high energies, of both π and σ electrons. The obtained maxima of the scattering cross sections correspond to the values of 20 and 27 eV that were determined experimentally and in quantum models for the maxima of the photoionisation cross sections of fullerenes C60 and C28, respectively. Approximate analytical results are presented for resonant frequencies, Q factors, radiation patterns, scattering and absorption cross sections for sphere-like particles and fullerenes, as well as integral equations and functionals for dielectric particles with a conducting shell of arbitrary shape. Analysis relies on the use of effective surface conductivity.

Investigation of the intershell higher order resonant recombination and polarization of X‐ray emission of B‐like silicon ions

K‐shell dielectronic, trielectronic, and quadruelectronic recombination and polarization of X‐ray emission have been studied for the highly charged Si9+ ions in the initial ground state 2P1/2 and the metastable state 2P3/2 using the Flexible Atomic Code. It is found that the resonant recombination cross section from the long‐lived metastable state is comparable in magnitude with that of the ground state, so it is important for plasma diagnostics. For Si9+(2P1/2), trielectronic recombination contributions of nearly 25% to the total resonant recombination strength are predicted, which is less than previous calculations. We compare the degree of linear polarization for the eleven dominant resonant recombination satellite lines from the initial parent Si9+(2P1/2) and Si9+(2P3/2) ions. For the same X‐ray lines, large variations of polarization are found between 2P1/2 and 2P3/2, which can be employed to diagnose formation mechanisms of intermediate resonance states and corresponding X‐ray lines.

Cross sections by electron impact excitation and ionization of tungsten ions, W39+

Excitation cross sections by electron impact of tungsten ions, W39+, have been calculated using R-matrix method for a configuration state list consists of [Ar]3d104s24p5, [Ar]3d104s24p44l, (l = d, f), and [Ar]3d104s24p45l′, l′ = s, p. A set of configuration state functions (CSFs) with 2-electron excitations up to 5l orbitals have been included within the MCDF-calculations of the used radial integrals of collisional excitations. R-matrix calculations of collision strength and cross section have been executed for the intercombination transitions between 4p5, 4p44d, and 4p44f at different angular momenta using DARC code. Resonance cross section have been observed at low energy of incident electron in the range of ∼5=-40 Ryd, however, the strong lines limited between 5 and 25 Ryd. The relativistic distorted-wave (DW) approximation, Coulomb–Born-Exchange (CBE) approximation, and the Binary-Encounter-Dipole (BED) theory have been used to calculate the electron impact ionization (EII) of the present ion. The accuracies of the present results are estimated by comparing R-matrix calculations with the available literature.

The appearances of the resonant spontaneous emission of ultrarelativistic electrons in the field of a nucleus and a laser

The contemporary theoretical investigation researches the resonant spontaneous bremsstrahlung (RSB) of ultrarelativistic electrons in the field of a nucleus and a laser. The considered process maintains prospect to progress in two observable reaction channels. The academic study scrutinizes specifically the resonant kinematics of the procedure mechanical development. The examination indicates a significant preponderance of one reaction channel over the second alternative. Moreover, the resonant differential cross section of the RSB prominently exceeds the corresponding differential cross section in the absence of the external field.

Impact of standard neutrino oscillations and systematics on proton lifetime measurements

We use atmospheric neutrino phenomenology to obtain the expected background to proton decay in large deep underground neutrino detector (DUNE)-like neutrino detectors. We introduced, for the first time in this kind of analysis, the experimentally confirmed neutrino oscillations of the atmospheric neutrino observations which reduce the corresponding background for the nucleon decay channel by a factor of 40%. Furthermore, we infer the impact of four systematics on such background: the overall efficiency, the muon reconstruction energy resolution, the resonant neutral pion cross-section, and the neutral pion angular resolution. Considering a 40 kton detector with efficiency of 45%, our analysis leads to an error band in the lower limit for the proton lifetime sensitivity, τ/B, from 7.9 × 1033 years to 1.1 × 1034 years at 90% confidence level (C.L.). These numbers can be compared with the current mode-dependent experimental limits τ > 1031 − 1033 years at 90% C.L.

Analysis of Categorical Subgroup Method for Resonance Self-Shielding Treatment

To meet the requirements of one step lattice calculation on resonance effect, a self-developed design and construction of a resonance treatment code are composed based on subgroup method and HELIOS-1.11 library. Subgroup fixed source equations are solved by method of characteristics to get subgroup fluxes, which are subsequently used to deduce effective resonance cross sections combined with subgroup weights and subgroup levels. Bondarenko method is employed to handle resonance interference effect and a resonance category scheme and resonance geometry simplification method are introduced to improve efficiency. Benchmarks of single pin cells and assemblies of light water reactor are adopted for numerical validation and the calculating results indicate that this method can treat resonance effect both precisely and effectively.

Расчет расщепления собственной частоты цилиндрического резонатора твердотельного волнового гироскопа на основе численного интегрирования высокой точности

Solid-state wave gyroscopes are widely used in various fields of technology. The principle of their operation is based on the phenomenon of precession of the elastic wave, which rotates at an angular velocity proportional to the angular velocity of device body rotation. The accuracy of the device is significantly affected by splitting the gyroscope resonator frequency. The article considers splitting caused by the distortion of the cylindrical resonator cross-section shape. Since the splitting is very small, the perturbation method is usually used to determine it. The article proposes a new method for calculating the splitting based on the numerical high accuracy integration of equations of dynamics of a cylindrical shell with a non-circular cross section. To search for two very close frequencies, through the difference of which the splitting was found, a linear boundary eigenvalue problem was solved with retention of a large number of decimal places. Examples of determining the natural frequency splitting are presented for various laws of the distribution of the radial deviation of the cavity cross-section shape along the circumferential coordinate. Verification of the results was performed by the finite element method. When using the method each of the two close frequencies was calculated with high accuracy

Search for Higgs boson pair production in the boverline{b}W{W}^{*} decay mode at sqrt{s} = 13 TeV with the ATLAS detector

A search for Higgs boson pair production in the boverline{b}W{W}^{*} decay mode is performed in the boverline{b}mathit{ell nu qq} final state using 36.1 fb−1 of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of events beyond the background expectation is found. Upper limits on the non-resonant pp → HH production cross section of 10 pb and on the resonant production cross section as a function of the HH invariant mass are obtained. Resonant production limits are set for scalar and spin-2 graviton hypotheses in the mass range 500 to 3000 GeV.

Relativistic R-matrix photoionization cross section calculations of Ne-like Co XVIII with resonance parameters

We report total photoionization cross sections of the ground state and the first three excited states () of Ne-like Co XVIII ion using the close-coupling Breit–Pauli R-matrix (BPRM) approximation. The target wavefunctions are constructed by configuration interaction technique (CIV3). Our calculated ionization threshold energies for the ground and excited states show a good agreement with the NIST ones. To further affirm the accuracy and reliability of our BPRM results, photoionization cross section calculations for the ground state have also been performed by employing the fully relativistic Dirac Atomic R-matrix Code. Our two independent calculations show a reasonable agreement both in magnitude and resonant photoionization cross sections. The resonance positions (Er), widths (Γ) and quantum defects (μ) due to ejection of a 2p or 2s electron from the ground state are given by adopting Quigley and Berrington method. We believe that our cross section data may be beneficial for the modelling and diagnostics of astrophysical plasmas.

Model independent top quark width measurement using a combination of resonant and nonresonant cross sections

Though top quark was discovered more than twenty years ago, measurement of its width is still challenging task. Most measurements either have rather low precision or they are done in assumption of the SM top quark interactions. We consider model independent parametrization of the top quark width and provide estimations on achievable accuracy using a combination of fiducial cross sections in double, single and non-resonant regions.

Weak Exciton–Phonon Coupling in CdSe Nanoplatelets from Quantitative Resonance Raman Intensity Analysis

Resonance Raman spectra, cross sections, and depolarization ratios have been measured for 4.5 monolayer thick CdSe nanoplatelets dispersed in chloroform. Five excitation wavelengths between 514.5 and 476.5 nm were employed. The resonance Raman spectra are dominated by the longitudinal optical (LO) phonon near 201 cm–1 and its overtone, as in CdSe quantum dots. The absolute scattering intensity is much higher for excitation on resonance with the sharp, lowest-energy heavy-hole to conduction band transition than with higher energy transitions, decreasing by about a factor of 30 between 514.5 and 496.5 nm excitation. The LO phonon overtone is weak directly on resonance with the heavy-hole transition but much stronger at higher excitation energies, a result that is reproduced by simulations of the spectra using standard resonance Raman intensity theory. The absolute Raman cross sections imply a Huang–Rhys parameter for the LO phonon of about 0.08 on resonance with the lowest heavy-hole transition. This is a f...

Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb[over ¯]τ^{+}τ^{-} Decay Channel in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector.

A search for resonant and nonresonant pair production of Higgs bosons in the bb[over ¯]τ^{+}τ^{-} final state is presented. The search uses 36.1 fb^{-1} of pp collision data with sqrt[s]=13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. Decays of the τ-lepton pairs with at least one τ lepton decaying to final states with hadrons and a neutrino are considered. No significant excess above the expected background is observed in the data. The cross-section times branching ratio for nonresonant Higgs boson pair production is constrained to be less than 30.9fb, 12.7 times the standard model expectation, at 95%confidence level. The data are also analyzed to probe resonant Higgs boson pair production, constraining a model with an extended Higgs sector based on two doublets and a Randall-Sundrum bulk graviton model. Upper limits are placed on the resonant Higgs boson pair production cross-section times branching ratio, excluding resonances X in the mass range 305 GeV<m_{X}<402 GeV in the simplified hMSSM minimal supersymmetric model for tanβ=2 and excluding bulk Randall-Sundrum gravitons G_{KK} in the mass range 325 GeV<m_{G_{KK}}<885 GeV for k/M[over ¯]_{Pl}=1.

Application of the SPH method to account for the angular dependence of multigroup resonant cross sections in thermal reactor calculations

The issue of the angular dependence of the multigroup total cross sections in the multigroup transport equation solution was recognized a long time ago. Only recently has its impact on resonant self-shielding been identified. A viable solution for this problem is the superhomogenization (SPH) corrections. In the present work, two applications of the SPH method are presented, one applying to the APOLLO3® deterministic calculations with the multigroup cross sections condensed from the TRIPOLI-4® Monte Carlo simulation results and the other applying to a subgroup method based on the fine-structure equation. The numerical results show the effectiveness of the SPH method in dealing with this difficulty in both situations. This work also demonstrates that the subgroup method based on the fine-structure equation plus the SPH corrections is a practical, effective and accurate resonant self-shielding solution for the PWR fuel pin-cell and fuel assembly calculations.

Plasma losses from mirror trap, initiated by microwave radiation under electron cyclotron resonance conditions

Plasma of a stationary electron cyclotron resonance (ECR) discharge sustained by gyrotron radiation at a frequency of 24 GHz and a power of up to 300 W in a mirror magnetic trap was studied. At pressures near the gas breakdown threshold, the extinction effect of an electron cyclotron discharge is observed with increasing radiation power. When the cyclotron resonance cross-section approaches the magnetic plug, the power threshold corresponding to the discharge extinction decreases. These experimental results confirm the presence of the effect of particles precipitation from the trap as a result of ECR interaction with gyrotron radiation. The experimental scaling of the extinction power dependence on the position of the ECR cross-section in a magnetic trap corresponds to the results of the estimates on the basis of the theory of particle precipitation in the quasilinear diffusion regime.

Search for narrow and broad dijet resonances in proton-proton collisions at sqrt{s}=13 TeV and constraints on dark matter mediators and other new particles

Searches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at sqrt{s}=13 TeV corresponding to an integrated luminosity of up to 36 fb−1. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W′ bosons below 3.3 TeV, Z′ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.

Different manifestations of S-matrix poles

Making use of the analytical properties of the S-matrix and a theorem of Mittag-Leffler, model independent non-relativistic expressions for cross sections in single channel elastic scattering, scattering phase shifts and survival probabilities of resonances are derived. Provided certain conditions are satisfied by the poles, the residues can also be estimated analytically. Considerations of the low energy behaviour of the S-matrix and cross sections reveal additional conditions on the residues of the poles appearing in the Mittag-Leffler expansions. The exact expressions for the resonant cross section and phase shift are shown to reduce to the commonly used Breit–Wigner formula plus corrections. The latter is shown to approach the exact result with the example of a meson and a baryon resonance. Finally, a comparison of the exact expressions with some realistic examples is presented. The calculations of survival probabilities in particular reveal the reason behind the non-observability of non-exponential decay.

Resonant excitation cross-sections of erbium in freestanding GaN bulk crystals

Erbium doped GaN (Er:GaN) is a promising candidate as a new gain medium for high energy lasers. The excitation and emission mechanisms as well as the transition cross sections of the pump and laser wavelength are of paramount importance for understanding the performance of lasers and amplifiers made of Er:GaN materials. We report here the results of direct measurements of resonantly excited photoluminescence emission, photoluminescence excitation, and optical absorption spectroscopy in the 1.5 μm “retina-safe” spectral region performed on freestanding Er:GaN bulk crystals synthesized by hydride vapor phase epitaxy. The results established that 1514 nm and 1538 nm are the most appropriate resonant pump wavelengths for achieving gain and lasing, which differs from Er in YAG and glass hosts. The absorption coefficients (α) and absorption cross-sections (σexc) of Er in GaN in the 1.5 μm window have been directly measured, providing σexc = 1.4 × 10−20 cm2 and 2.7 × 10−20 cm2 for 1514 nm and 1538 nm pump wavelengths, respectively. These values are considerably higher than those of Er ions in glass and YAG hosts.

Sub-TeV quintuplet minimal dark matter with left-right symmetry

A detailed study of a fermionic quintuplet dark matter in a left-right symmetric scenario is performed in this article. The minimal quintuplet dark matter model is highly constrained from the WMAP dark matter relic density (RD) data. To elevate this constraint, an extra singlet scalar is introduced. It introduces a host of new annihilation and co-annihilation channels for the dark matter, allowing even sub-TeV masses. The phenomenology of this singlet scalar is studied in detail in the context of the Large Hadron Collider (LHC) experiment. The production and decay of this singlet scalar at the LHC give rise to interesting resonant di-Higgs or diphoton final states. We also constrain the RD allowed parameter space of this model in light of the ATLAS bounds on the resonant di-Higgs and diphoton cross-sections.

Resonant parametric interference effect in spontaneous bremsstrahlung of an electron in the field of a nucleus and two pulsed laser waves

Resonant spontaneous bremsstrahlung of an electron scattered by a nucleus in the field of two moderately strong pulsed laser waves is studied theoretically. The process is studied in detail within the interference kinematic region. This region is determined by scattering of particles in the same plane at predetermined angles, at that stimulated absorption and emission of photons of external pulsed waves by an electron occurs in correlated manner. The correspondence between the emission angle and the final-electron energy is established in the kinematic region where the resonant parametric interference effect is manifested. The resonant differential cross section of ENSB process with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron, can exceed by 4-5 orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of ENSB in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross section in the Bunkin-Fedorov kinematic region. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (SLAC, FAIR, XFEL, ELI).

Wavelength-Dependent Third-Harmonic Generation in Plasmonic Gold Nanoantennas: Quantitative Determination of the d-Band Influence

Plasmonic gold nanoantennas are highly efficient nanoscale nonlinear light converters. The nanoantennas provide large resonant light interaction cross sections as well as strongly enhanced local fields. The actual frequency conversion, however, takes places inside the gold volume and is thus ultimately determined by the microscopic gold nonlinearity, which has been found to significantly surpass common bulk nonlinear materials. While the influence of the nanoantenna geometry and hence the plasmonic resonance has been studied in great detail, only little attention has been paid to the microscopic material nonlinearity. Here we show that the microscopic third-order nonlinearity of gold is in fact a resonant one by virtue of interband transitions between the d- and sp-bands. Utilizing a large set of resonant nanoantennas and a fiber-feedback optical parametric oscillator as a broadband-tunable light source, we show that the radiated third-harmonic signals significantly increase at the onset of interband tran...