A precision mass investigation of the neutron-rich titanium isotopes ^{51-55}Ti was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the ...N=32 shell closure, and the overall uncertainties of the ^{52-55}Ti mass values were significantly reduced. Our results conclusively establish the existence of the weak shell effect at N=32, narrowing down the abrupt onset of this shell closure. Our data were compared with state-of-the-art ab initio shell model calculations which, despite very successfully describing where the N=32 shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned multiple-reflection time-of-flight mass spectrometer, substantiated by independent measurements from TITAN's Penning trap mass spectrometer.
Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the Z=20 and 28 proton shell ...closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron-rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our high-precision mass measurements of 59,61−63Cr confirm previous results, and the improved precision in measurements of 64−65Cr refine the mass surface beyond N=40. With the ab initio in-medium similarity renormalization group, we examine the trends in collectivity in chromium isotopes and give a complete picture of the N=40 island of inversion from calcium to nickel.
We report high-precision mass measurements of ^{50-55}Sc isotopes performed at the LEBIT facility at NSCL and at the TITAN facility at TRIUMF. Our results provide a substantial reduction of their ...uncertainties and indicate significant deviations, up to 0.7 MeV, from the previously recommended mass values for ^{53-55}Sc. The results of this work provide an important update to the description of emerging closed-shell phenomena at neutron numbers N=32 and N=34 above proton-magic Z=20. In particular, they finally enable a complete and precise characterization of the trends in ground state binding energies along the N=32 isotone, confirming that the empirical neutron shell gap energies peak at the doubly magic ^{52}Ca. Moreover, our data, combined with other recent measurements, do not support the existence of a closed neutron shell in ^{55}Sc at N=34. The results were compared to predictions from both ab initio and phenomenological nuclear theories, which all had success describing N=32 neutron shell gap energies but were highly disparate in the description of the N=34 isotone.
Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular, for the determination of the appearance or disappearance ...of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti, and V isotopes performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) and the Low Energy Beam and Ion Trap (LEBIT) facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, 8 of which represent increases in precision over previous measurements. These measurements refine trends in the mass surface around N=32 and N=34, and support the disappearance of the N=32 shell closure with increasing proton number. Additionally, our data do not support the presence of a shell closure at N=34.
New mass values measured with the TITAN MR-TOF-MS are reported for the short-lived isotopes 24−26Ne, produced at TRIUMF's ISAC facility using a uranium carbide target and cold FEBIAD ion source. A ...least-squares adjustment within the framework of the Atomic Mass Evaluation was performed and the improved precision of the new mass values is highlighted. The improved mass accuracy in this N=14 mid-shell region can also point to the refinement in values of the charge radii. By reducing the mass uncertainty of isotopes, their contribution of the mass shift uncertainty in laser spectroscopy can be negated. The work is part of developments for reaching the N=20 Island of Inversion, where high molecular contamination hinders mass measurements of the neon isotopes.
Multiple-reflection time-of-flight mass spectrometers (MR-TOF-MS) have been demonstrated to have a mass resolving power in the range of few hundreds of thousand. The TITAN MR-TOF-MS has been used to ...separate isobaric impurities and measure masses of many rare isotopes. Recently we have measured the mass and half-lives of neutron-rich Rubidium isotopes with the MR-TOF-MS. This technique is capable of measuring the half-life of rare isotopes in the range of few tens of millisecond. In this proceeding, we present the measurement of half-life of 100Rb that was found to be 50±5 ms, in good agreement with literature value of 48±3 ms.
TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) has specialized in fast Penning Trap mass spectrometry of very short-lived radioactive isotopes. The facility has been upgraded with a ...Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) to continue its quest towards more exotic nuclides, which are critical for our understanding of nuclear structure effects far from the valley of beta stability and for the nucleosynthesis of heavy elements in explosive astrophysical environments. In this publication, we discuss the implementation, operation and performance of TITAN’s MR-TOF-MS as a stand-alone high-precision mass spectrometer and as an isobar separator. By using the novel mass-selective re-trapping technique for the isobar separation, the MR-TOF-MS can consecutively perform separation and mass measurement of the same ion population, acting as its own isobar separator. The device boosts the dynamic range and reach of the TITAN facility by several orders of magnitude. The MR-TOF-MS reaches a high mass resolving power (m/Δm∼400000), high precision and mass accuracy (δm/m<10−7), is fast (common cycle time 20ms), shows high sensitivity and very large dynamic range (ion of interest to contaminant ratios of up to 1 to 106).
A new series of neutron-rich indium mass measurements is reported from the TITAN multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). These mass measurements cover 125-134In (N = 76–85) ...and include ground states as well as isomeric states. The masses of nuclei in this region are known to be of great importance for accurately modeling r-process nucleosynthesis, and the significance of the reported neutron-rich indium masses is discussed in this context. Results are compared with earlier experimental data where available as well as theoretical mass models. The measurements reported here include the first mass measurements of 133,134In, as well as the first direct mass measurement of 132In. The masses of 125-131In ground states and several isomers were previously measured to higher precision by Penning trap mass spectrometry, which also resolved some low-lying isomers that could not be resolved in this work. The earlier Penning trap measurements serve as excellent cross-checks for the MR-TOF-MS measurements, and in some cases the MR-TOF-MS measurements improve the literature uncertainties of higher-lying isomer masses and excitation energies. Finally, a new isomeric state for 128In, recently reported for the first time by the JYFLTRAP group, is also confirmed by the TITAN MR-TOF-MS, with a measured excitation energy of 1813(17) keV.
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