Shell model analysis of the $ B(E2,2^+ \rightarrow 0^+)$'s in the A=70 T=1 triplet

Abstract: he $B(E2,2^+ \rightarrow 0^+)$ transition strengths of the T=1 isobaric triplet $^{70}$Kr, $^{70}$Br, $^{70}$Se, recently measured at RIKEN/RIBF, are discussed in terms of state of the art large scale shell model calculations using the JUN45 and JUN45+LNPS plus Coulomb interactions. In this letter we argue that, depending on the effective charges used, the calculations are either in line with the experimental data within statistical uncertainties, or the anomaly happens in $^{70}$Br, rather than $^{70}$Kr. In the latter case, we suggest that it can be due to the presence of a hitherto undetected 1$^+$ T=0 state below the yrast 2$^+$ T=1 state. Our results do not support a shape change of $^{70}$Kr with respect to the other members of the isobaric multiplet.