Abstract

We report on the $\beta$-delayed neutron emission probability (${P1n}_{1n}$) measurements of the $82,83,84\mathrm{Ga}$ ($N=51,52,53$) precursors performed in one single experiment using the $3\mathrm{He}$ neutron-counter TETRA at the ALTO facility in Orsay. Altogether our results for the three $A=82,83$, and 84 Ga precursors point towards a sizable ${P1n}_{1n}$ staggering in the $N=50$ region, similar to the one already observed just after the $N=28$ shell closure in the K isotopes chain, hinting at a similar mechanism. We will discuss the possible microscopic origin of this behavior, i.e., the existence in the light $N=51$ isotones of low-lying components of the so called pygmy Gamow-Teller resonance, already well established at $Z=36$, and persisting toward $79\mathrm{Ni}$.