Pygmy Gamow-Teller resonance in the N = 50 region: New evidence from staggering of β -delayed neutron-emission probabilities

We report on the β-delayed neutron emission probability (P1n) measurements of the Ga82,83,84 (N=51,52,53) precursors performed in one single experiment using the He3 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 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 Ni79.