Decay properties of ^68,69,70Mn: Probing collectivity up to N = 44 in Fe isotopic chain

Abstract

The β decays ${}^{68}\mathrm{Mn}\to {}^{68}\mathrm{Fe}$, ${}^{69}\mathrm{Mn}\to {}^{69}\mathrm{Fe}$ and ${}^{70}\mathrm{Mn}\to {}^{70}\mathrm{Fe}$ have been measured at the RIBF facility at RIKEN using the EURICA γ spectrometer combined with an active stopper consisting of a stack of Si detectors. The nuclei were produced as fission fragments from a beam of ²³⁸U at a bombarding energy of 345 MeV/nucleon impinging on a Be target and selected using the BigRIPS separator. Half-lives and β-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in ^69,70Fe. The data indicate a continuously increasing deformation for Fe isotopes up to $\mathrm{A}=70$. This is interpreted, as for Cr isotopes, in terms of the interplay between the quadrupole correlations of the $\nu 1{\mathrm{d}}_{5/2}$ and $\nu 0{\mathrm{g}}_{9/2}$ orbitals and the monopole component of the $\pi 0{\mathrm{f}}_{7/2}\text{–}\nu 0{\mathrm{f}}_{5/2}$ interaction.