Fast Timing Study of the β− Decay of 63Mn to 63Fe

International audienceThe β− decay of 63Mn to 63Fe has been studied in an experiment at ISOLDE, CERN. The previously known 63Fe level scheme has been confirmed and greatly expanded, to a total of 31 levels and 73 γ lines. The energy of the 9/2+ isomer state has been measured for the first time at 475.0 keV, completing the systematics of such states in odd-Fe isotopes below 68Ni. In addition, the lifetimes of the low-lying states have been measured, allowing the tentative assignment of the spin-parity sequence for those levels

Beta decay of 66^{66}Mn to the N=40N = 40 nucleus 66^{66}Fe

International audienceThe low energy structure of 66Fe was studied by means of γ- and fast-timing spectroscopy at the ISOLDE/CERN facility. The level scheme of 66Fe populated following the ${\beta }^{-}$ decay of 66Mn was established. It confirms and further expands the level scheme from recent publications. The β-delayed neutron emission branch was measured and γ rays in 65Fe were observed following the β–n decay for the first time. The half lives of the ${2}_{1}^{+}$ state and four other states of 66Fe were measured using the advanced time-delayed $\beta \gamma \gamma$(t) method. These results are compared with large-scale shell-model calculations based on the Lenzi–Nowacki–Poves–Sieja interaction. The β-decay of 66Mn to 66Fe has been calculated as well, and log(ft) values derived. Spin and parity assignments are proposed based on the experimental information and the new calculations

Search for shape-coexisting 0+^+ states in 66^{66}Ni from lifetime measurements

International audienceThe lifetime of the 0$_3^+$ state in $^{66}$Ni, two neutrons below the $N=40$ subshell gap, has been measured. The transition $B(E2;0_3^+ \rightarrow 2_1^+)$ is one of the most hindered E2 transitions in the Ni isotopic chain and it implies that, unlike $^{68}$Ni, there is a spherical structure at low excitation energy. We have performed extensive shell-model calculations that correctly predict this result, obtaining a spherical 0$^+$ state at the correct energy and with an extremely low $B(E2;0_3^+ \rightarrow 2_1^+)$ value

Fast-timing study of Ga 81 from the β decay of Zn 81

The β− decay of 81Zn to the neutron magic N=50 nucleus 81Ga, with only three valence protons with respect to 78Ni, was investigated. The study was performed at the ISOLDE facility at CERN by means of γ spectroscopy. The 81Zn half-life was determined to be T1/2=290(4) ms while the β-delayed neutron emission probability was measured as Pn=23(4)%. The analysis of the β-gated γ-ray singles and γ−γ coincidences from the decay of 81Zn provides 47 new levels and 70 new transitions in 81Ga. The β−n decay of 81Zn was observed and a new decay scheme into the odd-odd 80Ga nucleus was established. The half-lives of the first and second excited states of 81Ga were measured via the fast-timing method using LaBr3(Ce) detectors. The level scheme and transition rates are compared to large-scale shell-model calculations. The low-lying structure of 81Ga is interpreted in terms of the coupling of the three valence protons outside the doubly magic 78Ni core

Search for the 73Ga^{73}\mathrm{Ga} ground-state doublet splitting in the β\beta decay of 73Zn^{73}\mathrm{Zn}

International audienceThe existence of two close-lying nuclear states in $^{73}$Ga has recently been experimentally determined: a 1/2$^−$ spin-parity for the ground state was measured in a laser spectroscopy experiment, while a J$^{\pi} = 3/2^−$ level was observed in transfer reactions. This scenario is supported by Coulomb excitation studies, which set a limit for the energy splitting of 0.8 keV. In this work, we report on the study of the excited structure of $^{73}$Ga populated in the $\beta$ decay of $^{73}$Zn produced at ISOLDE, CERN. Using $\beta$-gated, $\gamma$-ray singles, and $\gamma - \gamma$ coincidences, we have searched for energy differences to try to delimit the ground-state energy splitting, providing a more stringent energy difference limit. Three new half-lives of excited states in $^{73}$Ga have been measured using the fast-timing method with LaBr$_3$(Ce) detectors. From our study, we help clarify the excited structure of $^{73}$Ga and we extend the existing $^{73}$Zn decay to $^{73}$Ga with 8 new energy levels and 35 $\gamma$ transitions. We observe a 195-keV transition consistent with a $\gamma$ ray de-exciting a short-lived state in the $\beta$-decay parent $^{73}$Zn

Low-lying isomeric states in 80Ga from the β− decay of 80Zn

A new level scheme of Ga-80 has been determined. This nucleus was populated following the beta(-) decay of Zn-80 at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s beta(-)-decaying 6(-) isomer is the ground state of 80Ga and the 1.3-s beta(-)-decaying 3(-) isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions