E. Minaya Ramirez

Direct Mapping of Nuclear Shell Effects in the Heaviest Elements

Pinning Down Nuclear Shells The nuclei of heavy atoms are destabilized by proton repulsions, and, conversely, the quantum-mechanical shell effects help to stabilize them. There are theoretical models for predicting the masses of yet-to-be-discovered superheavy elements, based on such shell effects, and these models can be tested by studying the shells of known actinide nuclei. The problem is that current mass values determined from studying radioactive decay products have substantial errors. Minaya Ramirez et al. (p. 1207, published online 9 August; see the Perspective by Bollen) were able to collect a sufficient number of nuclei of lawrencium and nobelium isotopes in an ion trap to determine their masses directly by mass spectroscopy. These results will be helpful in predicting the heaviest possible element. Highly precise mass measurements of nobelium and lawrencium isotopes provide insight into superheavy element stability. Quantum-mechanical shell effects are expected to strongly enhance nuclear binding on an “island of stability” of superheavy elements. The predicted center at proton number Z = 114, 120, or 126 and neutron number N = 184 has been substantiated by the recent synthesis of new elements up to Z = 118. However, the location of the center and the extension of the island of stability remain vague. High-precision mass spectrometry allows the direct measurement of nuclear binding energies and thus the determination of the strength of shell effects. Here, we present such measurements for nobelium and lawrencium isotopes, which also pin down the deformed shell gap at N = 152.

Precision Measurement of the First Ionization Potential of Nobelium

One of the most important atomic properties governing an elements chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626 21±0.000 05  eV. This work provides a stringent benchmark for state-of-the-art many-body atomic modeling that considers relativistic and quantum electrodynamic effects and paves the way for high-precision measurements of atomic properties of elements only available from heavy-ion accelerator facilities.

Neutron Drip-Line Topography

The development of microscopic mass models is a crucial ingredient for the understanding of how most of the elements of our world were fabricated. Confidence in drip‐line predictions of such models requires their comparison with new mass data for nuclides far from stability. We combine theory and experiment using results that are state of the art: the latest mass measurements from the Penning‐trap spectrometer ISOLTRAP at CERN‐ISOLDE are used to confront the predictions of the latest Skyrme‐Hartree‐Fock‐Bogoliubov (HFB) microscopic mass models. In addition, we compare the new data to predictions of other types of mass models and the extrapolative behavior of the various models is analyzed to highlight topographical trends along the shores of the nuclear chart.

Extending Penning trap mass measurements with SHIPTRAP to the heaviest elements

Penning-trap mass spectrometry of radionuclides provides accurate mass values and absolute binding energies. Such mass measurements are sensitive indicators of the nuclear structure evolution far away from stability. Recently, direct mass measurements have been extended to the heavy elements nobelium (Z=102) and lawrencium (Z=103) with the Penning-trap mass spectrometer SHIPTRAP. The results probe nuclear shell effects at N=152. New developments will pave the way to access even heavier nuclides.

Probing the nuclides {sup 102}Pd, {sup 106}Cd, and {sup 144}Sm for resonant neutrinoless double-electron capture

The Q values for double-electron capture in {sup 102}Pd, {sup 106}Cd, and {sup 144}Sm have been measured by Penning-trap mass spectrometry. The results exclude at present all three nuclides from the list of suitable candidates for a search for resonant neutrinoless double-electron capture.

Q values for neutrinoless double-electron capture in {sup 96}Ru, {sup 162}Er, and {sup 168}Yb

The

Phase-imaging ion-cyclotron-resonance measurements for short-lived nuclides.

Q

Octupolar-Excitation Penning-Trap Mass Spectrometry for Q-Value Measurement of Double-Electron Capture in164Er

values of the neutrinoless double-electron capture transitions in

Plumbing Neutron Stars to New Depths with the Binding Energy of the Exotic Nuclide82Zn

{}^{96}\text{Ru}

Resonant Enhancement of Neutrinoless Double-Electron Capture in 152Gd

,