Exploring magicity around N = 32 & 34 in Z >= 20 isotopes via precision mass measurements and developments with the TITAN MR-TOF mass spectrometer

The Nuclear Shell Model provided the first coherent description of the nucleus which accounted for a wide range of nuclear properties. The model originated from observations of particularly stable isotopes with certain numbers, known as `magic numbers’, of protons and neutrons. At the time it was developed, in the 1960s, observations were limited to naturally occurring, and therefore stable, isotopes. With the advent of radioactive beam facilities, new studies indicate that the magic numbers seem to evolve and model corrections are required. In this thesis, the TITAN Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) was employed to study `new' magic numbers N=32,34 across a range of isotopic chains about the traditionally magic Z=20. This work includes a characterisation of the TITAN MR-TOF-MS and high-precision mass measurements of 54Ca, 54,55Sc, 54-56Ti, and 54-58V. Isotopes of neutron-rich Ca, Sc, Ti and V were produced at the TRIUMF-ISAC facility and transported to the TITAN facility for measurement. The results show magicity at N=32 is at a maximum in 52Ca, and the effects decrease with increasing Z across the isotopes measured, the effects are slightly weaker in 53Sc, and cease between 54Ti and 55V. This evolution is dramatically different due to the new measurements of 54,55Sc. The precision on the masses of all isotopes measured in the study is improved in comparison to the AME2016, and results include the first ever direct mass measurement of 58V. The evolution of N=32,34 magicity is explored via these new high-precision mass measurements

Mass Measurements of Neutron-Deficient Yb Isotopes and Nuclear Structure at the Extreme Proton-Rich Side of the N=82 Shell

International audienceHigh-accuracy mass measurements of neutron-deficient Yb isotopes have been performed at TRIUMF using TITAN’s multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). For the first time, an MR-TOF-MS was used on line simultaneously as an isobar separator and as a mass spectrometer, extending the measurements to two isotopes further away from stability than otherwise possible. The ground state masses of Yb150,153 and the excitation energy of Ybm151 were measured for the first time. As a result, the persistence of the N=82 shell with almost unmodified shell gap energies is established up to the proton drip line. Furthermore, the puzzling systematics of the h11/2-excited isomeric states of the N=81 isotones are unraveled using state-of-the-art mean field calculation

High-precision mass measurement of neutron-rich 96Kr

International audienceWhile the nuclear deformation in the region around Z = 40 and N = 60 has been studied in great detail, the possible onset of nuclear deformation in the isotopic chain of krypton (Z = 36) is still a subject of controversy. Here, we present a high-precision mass measurement of the neutron-rich nuclide $^{96}$Kr, as measured by the Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN). A statistical method, based on a hyper-exponentially modified Gaussian, has been employed to model the data. As such, the uncertainty introduced by overlapping peaks from beam contaminants was reduced and the mass excess of $^{96}$Kr determined to be -53097(57)keV. The capability of the method has been confirmed with measurements of the stable isotopic pair $^{40}$Ar/$^{40}$Ca, in which a relative accuracy Δm/m of 3.5 ⋅ 10$^{− 8}$ and a mass resolving power of more than 400000 were achieved