Unusual Isospin-Breaking and Isospin-Mixing Effects in theA=35Mirror Nuclei

Abstract

Excited states have been studied in 35Ar following the 16O(24Mg,1alpha1n)35Ar fusion-evaporation reaction at 60 MeV using the Ge-detector array GASP. A comparison with the mirror nucleus 35Cl shows two remarkable features: (i) A surprisingly large energy difference for the 13/2(-) states, in which the hitherto overlooked electromagnetic spin-orbit term is shown to play a major role, and (ii) a very different decay pattern for the 7/2(-) states, which provides direct evidence of isospin mixing.

Isospin symmetry in the odd-odd mirror nuclei44V/44Sc

“…There is no evidence in this region for any significant asymmetry in M1 decay patterns between mirror nuclei, therefore the observed asymmetry must be due to the E1 transitions. Despite the fact that isospin rules dictate that the B(E1) should be identical in mirror nuclei, some cases of strong asymmetries in B(E1) strengths have been indicated by recent data, especially in the A = 35 [34] and A = 31 [35] mirror pairs, and the factor of 40 here does not seem out of line. A summary of the current situation regarding these asymmetries is given by Pattabiraman et al [36] where factors ranging from 40 to 50 were also presented.…”

Mass of astrophysically relevantCl31and the breakdown of the isobaric multiplet mass equation

“…Interestingly, the cubic coefficients for the A = 31 [d = −3.5(11) keV] and A = 35 [d = −3.37(38) keV [13] ] J π = 3/2 + , T = 3/2 quartets are very similar, which motivates further theoretical studies of these neighboring members of the A = 4n + 3 series of the T = 3/2 quartets. Isospin mixing has been discussed for A = 35 [20,57] but no clear explanation for the breakdown has been given so far. Isospin mixing is plausible also for FIG.…”

Level structure ofS31: From low excitation energies to the region of interest for hydrogen burning in novae through theP30(Doherty1, Woods2, Lotay3 et al. 2014Phys. Rev. C200100View full textAdd to dashboardCite

“…are consistent with differences observed between γ -decay modes of mirror states reported in other sd-shell nuclei, e.g., Refs. [1,16]. Also shown, in Fig.…”

“…Nevertheless, if it does exist and is shown to be the analog of the 6399-keV level in 31 P, then a likely alternative 31 P analog for the 6160-keV state would be the 7/2 + , 6046-keV level, which, at present, is not paired with any state in 31 S. However, we note that such an assignment would imply a negative mirror energy difference (MED) of ∼100 keV, a value not observed for other states in this work or in other studies of 045804-6 sd-shell mirror nuclei, e.g., Refs. [1,16,18]. Consequently, the mirror-assignments presented in our previous work [5] are still favored.…”

“…Energy and efficiency calibrations were performed using standard 152 Eu and 56 Co sources. An additional 6.129-MeV line in 16 O, from the 13 C(α,n) 16 O reaction, was also used as a calibration point to improve the energy calibration for high-energy γ rays. The source data and 16 O transition were then also used to apply a correction for the known nonlinearity of the Gammasphere detector array, this step is crucial in obtaining accurate γ -ray energies, particularly for high energy γ rays.…”