Fine structure, partial widths and spreading widths of isobaric analogue resonances

Formulas for the microscopic calculation of partial widths and spreading widths, derived from several theories of the isobaric analogue resonances, are compared and critically examined. It is shown that the statistical assumptions used in the derivation of these formulas are not in contradiction with the fine-structure data, in contrast to recent speculations. The accuracy with which partial and spreading widths can be calculated is discussed. The theoretical values of the partial widths, and thus the determination of the spectroscopic factors, involve poorly known phenomenological parameters (essentially the shape of the symmetry potential). Thence, only relative values of the spectroscopic factors can at present be accurately determined. The calculation of the spreading width depends critically upon our knowledge of isospin violation in the nucleus. Recent calculations of the spreading widths are re-examined in the light of these results.     

Regularities and similarities in plasma broadened spectral line widths (Stark widths)

Regularities and similarities in plasma broadened line widths have been studied by a comprehensive analysis of existing experimental data. Regularities are expected on the basis of general atomic structure considerations, and should be evident for spectral series, for corresponding transitions in homologous atoms and in isoelectronic sequences. Furthermore, similarities of line widths are expected for multiplets, supermultiplets and, to a lesser degree, for transition arrays. A comprehensive examination of literature data has been undertaken, which shows generally a close adherence of the measured data to the expected regularities. A few notable exceptions are also given.     

Correlation widths in quantum-chaotic scattering

An important parameter to characterize the scattering matrix S   for quantum-chaotic scattering is the width Γcorr${\Gamma }_{\mathrm{corr}}$ of the S  -matrix autocorrelation function. We show that the “Weisskopf estimate” d/(2π)c_∑Tc$d/(2\pi ){\sum }_c{T}_c$ (where d   is the mean resonance spacing, Tc$T_c$ with 0?Tc?1$0?T_c?1$ the “transmission coefficient” in channel c   and where the sum runs over all channels) provides a good approximation to Γcorr${\Gamma }_{\mathrm{corr}}$ even when the number of channels is small. That same conclusion applies also to the cross-section correlation function.     

Measured Cd III Stark widths

The Stark FWHM (Full-Width at Half of the Maximal line intensity, W) have been measured for 16 doubly ionized cadmium (Cd III) spectral lines in a pulsed helium discharge in the wavelength interval between 200 nm and 304 nm. The helium discharge was created in the linear low pressure pulsed arc operated at 19 000 K electron temperature and 5.0×¹⁰²² m−3 electron density. The cadmium atoms were sputtered from the cadmium (99.9% purity) cylindrical plates located in the linear part of the discharge tube. The high density of the Cd III ions is boosted by cascade ionization processes via the well populated Cd II energy levels due to the Penning and charge exchange effects. The shapes of the Cd III lines are recorded using a spectrograph (McPherson model 209, 1.33 m focal-length with 2400 grooves/mm holographic grating) and intensified CCD camera (Andor DH740-18F-03) as a high-sensitive detection system. The Stark parameters introduced in this Letter are the first published experimental Cd III Stark widths.     

Pulse widths and time dilatation

The temporal widths of a light pulse as measured in different inertial frames are shown to have a relation more complicated than that of a simple time dilatation. The result is compared with the dilatation in the twin paradoxGedanken experiment. The light pulse measurement requires two observers in two different frames. The measurements of the observers are compared. For the twin experiment a comparison is made between two clocks which have undergone different histories between the two points at which their world lines intersect.     

Measurement of the boundary widths of iron,nickel, and iron-nickel films

Polycrystalline Fe, Ni, and Ni-Fe films have been studied by electron microscopy. The boundary widths have been measured as a function of the initial composition of the material evaporated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 7, pp. 70–73, July, 1969.     

The first Au III Stark widths

The shapes of 12 doubly ionized gold (Au III) spectral lines have been measured in the laboratory helium plasma at about 16 600 K electron temperature and 7.4×¹⁰²² m⁻³$7.4\times {10}^{22}{\text{ m}}^{\mathrm{-3}}$ electron density. At mentioned plasma conditions the Stark broadening has been found as the dominant mechanism in the Au III line shape formation. Here presented data are the first reported values for Stark widths related to the Au III lines. The modified version of the linear, low-pressure, pulsed arc was used as a plasma source operated in helium with gold atoms, as impurities, evaporated from gold cylindrical plates located in the homogeneous part of the discharge, providing conditions free of self-absorption.     

Fission widths and multi-dimensional barrier penetration

A multi-dimensional fission barrier is constructed which is simple enough to permit a complete partial-wave solution of the coupled-channel scattering problem. By employing it to study the multi-channel barrier resonances it produces, we discover that their widths are not directly related to any simple property of the elements of the transmission matrix, but rather to the eigenvalues of this matrix. Whenever one of these eigenvalues occurs near zero, it produces a resonance with an unexpectedly large width. In this sense, multi-dimensional barriers can cause an unforeseen “enhancement” of resonance widths.     

Phonon and magnon widths in metamagnets

Microscopic expressions for the couplings of the phonons corresponding to the rigid motions of the waters of hydration with both transverse and longitudinal spin fluctuations are given for the linear chain metamagnetic systems FeCl₂·2H₂O, CoCl₂·2H₂O, and CoBr₂·2H₂O. The processes which can give large, temperatures dependent widths of spin waves and of some phonons for temperatures approaching the Neél temperature are discussed.     

Charmonium decay widths in magnetized matter

The European Physical Journal A - In this paper, we investigated the spectroscopy of heavy tetraquarks through a relativistic diquark-antidiquark model. To this aim, the two-bosonic Klein-Gordon...     

Radiative widths of neutral kaon excitations

We observe 147 events of the axial vector pairK ₁(1270)–K ₁(1400) produced in the Coulomb field of a Pb target and measure the radiative widths Γ(K ₁(1400)→K ⁰ + γ) = 280.8 ±23.2(stat.) ±40.4(syst.) keV and Γ(K ₁(1270) →K ⁰ + γ) = 73.2 ±6.1(stat.) ±28.3(syst.) keV. These first measurements are lower than the quark-model predictions. We also place upper limits on the radiative widths forK*(1410) andK ₂ ^* (1430) and find that the latter is very small in accord withSU(3)invariance in the naive quark model.     

Electromagnetic perturbation of isobaric multiplet widths

The manner in which isobaric multiplet decay widths are modified by electromagnetic interaction is studied. Arguments based on lowest-order perturbation theory are given that the widths should be quadratic in T_z, if the multiplet is particle unstable in the absence of electromagnetism, but quartic for stable multiplets. The total widths of experimentally known multiplets are analyzed to determine their algebraic T_z, dependence and both quadratic and non-quadratic cases are found. On the basis of a simple model of the Coulomb energy we then determine the masses of these multiplets in the absence of electromagnetism as well as the masses of the lowest T-allowed decay channels. We find the isobaric multiplet width equation to work in some cases while it has been found to be inconclusive in others; because of these uncertainties as to its correctness or range of applicability, we have constructed a soluble model in which tests may be carried out. To avoid difficulties such as the many-body problem, a non-local separable potential model simple enough to solve explicitly was chosen. Although the model is an oversimplification of the real nuclear situation it has been found to work very well. Namely, the quadratic quartic nature of the widths was borne out in the model.     

Mechanisms and widths of two-proton decay

A method for calculating the widths of two-proton decay of nuclei with regard to its deep subbarrier character is proposed. The structure and coupling of the channels of facilitated two-proton decay of spherical nuclei are considered for the diproton and uncorrelated mechanisms of two-proton decay.     

Studies on the goodness of IBA group symmetries. I. Centroids,widths and partial widths for irreducible representations of IBA group symmetries

We present explicit analytic expressions for the centroids, widths and partial widths of the eigenvalue distribution over an irreducible representation corresponding to various group symmetries of the interacting boson approximation model of Arima and Iachello. As an example we present a study of the goodness of IBA group symmetries for Sm isotopes.