Shape Changes in the Mirror Nuclei Kr70 and Se70

Abstract

We studied the proton-rich Tz = −1 nucleus 70 Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2; 0 + → 2 +). Comparison with the other members of the A = 70 isospin triplet, 70 Br and 70 Se, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of Tz. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei 70 Kr and 70 Se contrary to the model predictions.

Information content of the differences in the charge radii of mirror nuclei

“…Those beyond-DFT corrections are quite significant for ∆R mir ch ( 54 Ni/Fe). In this context, we note that the observed B(E2) rates in mir- ror nuclei indicate the presence of strong isovector effects [54], which are likely to affect ∆R mir ch . It has been suggested in Ref.…”

“…It is only in the case of R skin in which the major axis of the correlation ellipsoid practically coincides with the systematic trend line that a near-perfect correlation is obtained that can be used for the parameter reduction. It is interesting to note the large CoD values around 0.86-0.88 (R L,∆R mir ch =0.93-0.94) that were obtained for ∆R mir ch in 54 Ni/Fe and other mirror pairs in Ref. [18].…”

“…Results.-To emphasize the need for using HFB in ∆R mir ch calculations, Table I lists the calculated proton Fermi levels for the proton-rich mirror partners considered in this work. These are all very weakly bound ( 36 Ca, 54 Ni) or unbound ( 48 Ni), which suggests that the proton continuum space can impact theoretical predictions, especially for radial properties [25]. To illustrate the relevance of the CoDs when analysing isovector indicators, Fig.…”

“…The values of ∆R mir ch for 36 Ca/S, 48 Ni/Ca, and 54 Ni/Fe mirror pairs calculated in BCS and HFB are shown in Fig. 3.…”

“…FIG.3. The mirror radius differences for (a)36 Ca/S, (b)48 Ni/Ca, and (c)54 Ni/Fe calculated with SV-min and FY(∆r) EDFs in BCS and HFB variants. The error bars indicate the statistical uncertainty associated with χ 2 optimization.…”