Search results for "pole [resonance]"
showing 10 items of 238 documents
Design of a Compact Dual Circular-Polarized Antenna for L-Band Satellite Applications
2020
In this paper, we propose the design of a dual circular-polarized antenna for L-band applications (1.1-1.6 GHz). The designed antenna has been developed by considering crossed-dipoles on top of which a circular patch has been placed to properly act on the mutual coupling between the dipoles. The dual circular polarization is achieved by feeding dipoles in quadrature. Moreover, to increase the antenna gain and polarization purity at high elevation angles, a fence of passive monopoles has been added. The proposed antenna can profitably used as primary feed of a low-frequency parabolic reflector.
Plasma Electron Kinetics and Distribution Functions in Laser Fields
2010
A concise review of the properties of electron distribution functions in a fully ionized plasma in the presence of a high-frequency laser field is presented. In detail is discussed the physical origin of most of the reported results in the case of strong fields. The presence of a laser field, through the inverse bremsstrahlung absorption, alters dynamically the roles of and the interplay between electron-ion and electron-electron collisions shaping the distribution function. Special attention is paid to the role of e-e collisions in the process of laser-plasma interaction.
Electromagnetic Multipole Moments and Transitions
2007
In the preceding chapter we constructed and discussed the simplest possible nuclear wave functions. This construction was done at the mean-field level. No account was taken of configuration mixing caused by the nuclear residual interaction. These simple wave functions produce degeneracies in energy spectra. This is contrary to experimental data, so improved wave functions are called for.
Observation of a unitary cusp in the thresholdγp→π0preaction
1997
A rigorous multipole analysis of the recent $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}p$ cross-section measurement is presented. The data were taken using the photon spectrometer TAPS at the tagged photon beam of the Mainz microtron. The $s$ and $p$ wave multipoles were extracted using minimal model assumptions. The predicted unitary cusp for the $s$-wave multipole ${E}_{0+}$ due to the two step $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}n\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}p$ reaction was observed. The results are consistent with one-loop chiral perturbation theory calculations for which three low-energy constants have been determi…
E1 andE2/E0 form factors and strength distributions fromSi28(e,e’p) andSi28(e,e’α) coincidence scattering
1986
A model-independent multipole analysis of $^{28}\mathrm{Si}$(e,e'p) and $^{28}\mathrm{Si}$(e,e'\ensuremath{\alpha}) coincidence data, taken at three momentum transfers 0.39lql0.68 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$, yields both E1 and E2/E0 form factors and the respective multipole strength distributions in the giant-resonance region of $^{28}\mathrm{Si}$ (${E}_{x}$=14--22 MeV). While the deduced E1 strength agrees well with previous results, the total extracted E2/E0 strength is about twice the value found with isoscalar projectiles indicating the presence of large isovector E2/E0 contributions in the region of the isoscalar E2/E0 giant resonances.
Comment on "Highly nonlinear, sign-varying shift of hydrogen spectral lines in dense plasmas".
2004
The shift of hydrogen and hydrogenlike spectral lines in dense plasmas, calculated with the full computer simulation method, in nonquenching, classical path, dipole approximation for plasma-emitter interaction, is equal to zero. In the paper commented on, Escarguel et al., Phys. Rev. E 62, 2667 (2000) the electron concentrations ${N}_{e}$ and the corresponding temperature values T are shown to have been determined incorrectly.
States of167Ho from the decay of neutron rich nuclide167Dy
1977
Theβ −-decay of 66 167 Dy produced through the fast neutron reaction170Er(n, α)167Dy has been investigated by using several kinds of detectors and a high-capacity two-parameter recording system. The half-life andβ −-decay energy of167Dy were determined to beT 1/2 = 6.20 ± 0.08min andQ β-=2.35±0.06, respectively. The observed level scheme of 67 167 Ho (completely unknown previously) contains 12 states, among them a 6.0±0.1 μsM2 isomer at 259.3 keV. On the basis of theoretical and systematic considerations combined with multipole determinations, the following Nilsson model assignments are proposed for the lowest states of167Ho: 0 keV (7−/2 [523]), 259.3 keV (3+/2[411]), 319.8 keV (5/2 3+/2[41…
Virtual Compton scattering off the nucleon in chiral perturbation theory
1996
We investigate the spin-independent part of the virtual Compton scattering (VCS) amplitude off the nucleon within the framework of chiral perturbation theory. We perform a consistent calculation to third order in external momenta according to Weinberg's power counting. With this calculation we can determine the second- and fourth-order structure-dependent coefficients of the general low-energy expansion of the spin-averaged VCS amplitude based on gauge invariance, crossing symmetry and the discrete symmetries. We discuss the kinematical regime to which our calculation can be applied and compare our expansion with the multipole expansion by Guichon, Liu and Thomas. We establish the connectio…
Three-body Coulomb interaction effects in the final state of thePb208(B8,Be7p)Pb208Coulomb breakup reaction
2005
The photodissociation reaction $^{8}\mathrm{B}+\ensuremath{\gamma}\ensuremath{\rightarrow}^{7}\mathrm{Be}+p$ is used to provide information on the astrophysical ${S}_{17}$ factor of the inverse radiative capture reaction, knowledge of which is crucial for an estimation of the high-energy neutrino flux from the sun. Since, at present, the Coulomb field of a fully stripped nucleus serves as the source of the photons, an adequate analysis requires a genuine three-body treatment of this reaction. Among the uncertainties still affecting present analyses, the possible modification of the dissociation cross section by the post-decay acceleration of the fragments $^{7}\mathrm{Be}$ and p in the targ…
Multipole strength inC12from the (e,e’α) reaction for momentum transfers up to 0.61fm−1
1995
We have excited the giant resonance region in $^{12}\mathrm{C}$ via inelastic electron scattering, and have measured the first complete angular correlations for charged particle emission for this reaction for four values of momentum transfer ranging from 0.24 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ to 0.61 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. By analyzing the \ensuremath{\alpha}-emission channels via the Legendre and resonance formalisms, we unambiguously determined the multipole contributions to the total cross section for \ensuremath{\alpha} emission to the ground state of $^{8}\mathrm{Be}$, and have set limits on these contributions for \ensuremath{\alpha} emission to the first…