Isobaric Multiplet Yrast Energies and Isospin Nonconserving Forces

Abstract

The isovector and isotensor energy differences between yrast states of isobaric multiplets in the lower half of the pf region are quantitatively reproduced in a shell model context. The isospin nonconserving nuclear interactions are found to be at least as important as the Coulomb potential. Their isovector and isotensor channels are dominated by J=2 and J=0 pairing terms, respectively. The results are sensitive to the radii of the states, whose evolution along the yrast band can be accurately followed.

Isomeric mirror states as probes for effective charges in the lower pf shell

“…Using the notations and descriptions introduced in [12,14,15], multipole harmonic-oscillator Coulomb matrix elements, V CM , the monopole electromagnetic spin-orbit effect, V Cls , and a repulsive 100-keV term for the 1f 2 7/2 , J = 2 two-proton matrix element, V BM , are taken into account. The latter, chargeasymmetric component of the strong nucleon-nucleon interaction was suggested by [15] and supported by several measurements of specific energy differences of excited analogue states in pf -shell mirror nuclei (see, e.g., [50,51] and [12] for a recent review). More recently, an investigation based on the observation of core excited A = 54 analogue states confirmed this J = 2 two-proton matrix element representing the most relevant isospin-breaking component [52].…”

“…differences in excitation energies of analogue states, in a number of T z = ±1/2 mirror pairs and T z = 0, ±1 isospin triplets located between 40 Ca and 56 Ni on the chart of nuclei [12], and also beyond 56 Ni [13,14]. Proper descriptions of MED sequences in these pf -shell nuclei call for an isospin breaking part in the strong force [15,12], and there is an overall excellent quality of agreement in this mass regime between experiment and predictions based on modern large-scale shell-model approaches -with only few exceptions as pointed out in, for example, [16,17,18]. There have also been first attempts of shell-model calculations in larger model spaces, i.e., coupling 1d 3/2 particles to the pf shell [19] with significant progress towards full sd-pf calculations within the spherical shell-model and approaches based on density functional theory [20].…”

Isospin symmetry violation in mirrorE1transitions: Coherent contributions from the giant isovector monopole resonance in the67As-67<

“…A shell-model calculation in this Hilbert space could treat, on the same footing, both the regular (isovector) part of the E1 transition amplitude and the "induced-isoscalar" term originating from the mixing. In such a calculation, the isovector part of the two-body Coulomb interaction could be added to the empirical residual interactions, which could also include the symmetry-violating part necessary to account for the Coulomb energy differences [18].…”

Exotic Decay Modes in Rotating Nuclei

“…[26][27][28][29][30][31][32]), and this progress has been accompanied with detailed theoretical studies and refinements, for example, in Refs. [28,30,31,33]. Close to the center of the 1f 7/2 shell the observed mirror energy differences (MED) -the differences between level energies of adjacent states in pairs of mirror nuclei -are typically 10-100 keV, and they are (most often) readily explained by several Coulomb monopole and multipole effects.…”