D. Atanasov

Probing the N = 32 Shell Closure below the Magic Proton Number Z = 20: Mass Measurements of the Exotic Isotopes52,53K

The recently confirmed neutron-shell closure at N=32 has been investigated for the first time below the magic proton number Z=20 with mass measurements of the exotic isotopes (52,53)K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N=32, slightly lower than for 52Ca, highlighting the doubly magic nature of this nuclide. Skyrme-Hartree-Fock-Bogoliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.

Towards ultrahigh-resolution multi-reflection time-of-flight mass spectrometry at ISOLTRAP

The mass resolving power of the multi-reflection time-of-flight mass spectrometer of ISOLTRAP was studied by monitoring 39K+ signals. A drift tube at the center of the MR-ToF MS allows decreasing or increasing the kinetic energy of the ion bunch, by switching its potential when the ions are traversing it. This offers the possibility of capturing and ejecting ion bunches by controlling a single voltage by the so-called in-trap lift technique. It also allows changing the energy of the trapped ions inside the MR-ToF MS, offering a way to optimize the resolving power of the device. For a fixed number of 2000 laps corresponding to a total ion flight time of about 30 ms, data was accumulated for 100 experimental cycles, adding to a duration of 10 s for each spectrum. Without any subsequent corrections for broadening effects, mass resolving powers in excess of 300 000 (FWHM) were obtained.

Between atomic and nuclear physics: radioactive decays of highly-charged ions

Highly charged radioactive ions can be stored for extended periods of time in storage rings which allows for precision measurements of their decay modes. The straightforward motivation for performing such studies is that fully ionised nuclei or few-electron ions can be viewed as clean quantum-mechanical systems, in which the interactions of the many electrons can be either excluded or treated precisely. Thus, the influence of the electron shell on the decay probability can be investigated. Another important motivation is stellar nucleosynthesis, which proceeds at high temperatures and the involved atoms are therefore highly ionised. Presented here is a compact review of the relevant experiments conducted at heavy-ion storage rings. Furthermore, we outline the perspectives for future experiments at new-generation storage-ring facilities.

A resonant Schottky pickup for the study of highly charged ions in storage rings

A resonant Schottky pickup was built into the experimental storage ring at GSI Darmstadt in 2010 and a similar one in the CSRe storage ring at IMP Lanzhou in 2011. Single-ion sensitivity was achieved at 400 MeV u−1. The pickup has also been used in many storage ring experiments ever since. A brief description of the pickup and its application in single-ion lifetime spectroscopy is provided in this work.

arXiv : Study of the long-lived excited state in the neutron deficient nuclides

Direct mass measurements of the low-spin 3/2(-) and high-spin 13/2(+) states in the neutron-deficient isotopes Po-195 and Po-197 were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the nu i(13/2) orbital in Po-195,Po-197. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from alpha-decay chains. These excitation energies complete the knowledge of the energy systematics in the region and confirm that the 13/2(+) states remain isomeric, independent of the number of valence neutrons.

^{195,197,199}

The masses of the neutron-rich copper isotopes ^{75-79}Cu are determined using the precision mass spectrometer ISOLTRAP at the CERN-ISOLDE facility. The trend from the new data differs significantly from that of previous results, offering a first accurate view of the mass surface adjacent to the Z=28, N=50 nuclide ^{78}Ni and supporting a doubly magic character. The new masses compare very well with large-scale shell-model calculations that predict shape coexistence in a doubly magic ^{78}Ni and a new island of inversion for Z<28. A coherent picture of this important exotic region begins to emerge where excitations across Z=28 and N=50 form a delicate equilibrium with a spherical mean field.

Po by precision mass measurement

The masses of the neutron-rich copper isotopes ^{75-79}Cu are determined using the precision mass spectrometer ISOLTRAP at the CERN-ISOLDE facility. The trend from the new data differs significantly from that of previous results, offering a first accurate view of the mass surface adjacent to the Z=28, N=50 nuclide ^{78}Ni and supporting a doubly magic character. The new masses compare very well with large-scale shell-model calculations that predict shape coexistence in a doubly magic ^{78}Ni and a new island of inversion for Z<28. A coherent picture of this important exotic region begins to emerge where excitations across Z=28 and N=50 form a delicate equilibrium with a spherical mean field.

APS : Binding Energy of

The masses of the neutron-rich copper isotopes ^{75-79}Cu are determined using the precision mass spectrometer ISOLTRAP at the CERN-ISOLDE facility. The trend from the new data differs significantly from that of previous results, offering a first accurate view of the mass surface adjacent to the Z=28, N=50 nuclide ^{78}Ni and supporting a doubly magic character. The new masses compare very well with large-scale shell-model calculations that predict shape coexistence in a doubly magic ^{78}Ni and a new island of inversion for Z<28. A coherent picture of this important exotic region begins to emerge where excitations across Z=28 and N=50 form a delicate equilibrium with a spherical mean field.