First detailed structure information on the r-process path nucleus $^{63}$Fe

The nucleus $^{63}$Fe is located exactly at the point of transition between lighter Fe isotopes which show spherical structures and heavier Fe, where a sudden increase in quadrupole collectivity is manifested from lowering of the first excited 2$^{+}$ states in the even Fe nuclei. Very little is actually known on the exotic neutron-rich nuclei in this region. A substantial modification of the information on the nuclear structure of $^{63}$Fe and nuclei in its vicinity was obtained from a fast timing study conducted at the ISOLDE facility at CERN where levels in $^{63}$Fe were populated from the beta-decay of $^{63}$Mn. The new level scheme of $^{63}$Fe includes 21 gamma-transitions and 10 excited states. Although $^{63}$Fe seems to be understood in a shell model picture, a clear departure from spherical sequence is observed. From the measured log\textit{ft} values, gamma-ray branching ratios, and level half-lives in the ps range, we deduce spins and parities of 1/2$^{-}$, 3/2$^{-}$ and 5/2$^{-}$ for the lowest states in $^{63}$Fe which represent an inverted sequence in comparison to the heavier (and spherical) $N=37$ isotones, namely $^{65}$Ni and $^{67}$Zn.