Nuclear structure features of very heavy and superheavy nuclei—tracing quantum mechanics towards the ‘island of stability’

Abstract

The quantum-mechanic nature of nuclear matter is at the origin of the vision of a region of enhanced stability at the upper right end of the chart of nuclei, the so-called ‘island of stability’. Since the 1960s in the early second half of the last century, various models predict closed shells for proton numbers 114–126 and neutron numbers such as 172 or 184. Being stabilized by quantum-mechanic effects only, those extremely heavy man-made nuclear species are an ideal laboratory to study the origin of the strong nuclear interaction which is the driving force for matter properties in many fields ranging from microscopic scales like hadronic systems to cosmic scales in stellar environments like neutron stars. Since the 1950s, experiments on the synthesis of new elements and isotopes have also revealed various exciting nuclear structure features. The contribution of Bohr, Mottelson and Rainwater with, in particular, the development of the unified model played an essential role in this context. Although not anticipated in the region of the heaviest nuclei, many phenomena were subsequently discovered like the interplay of collective features manifesting themselves e.g. in nuclear deformation, ranging from spherical to prolate and oblate shapes with the possible occurrence of triaxial symmetries, and single particle states and their excitation into quasiparticle configurations. The continuous development of modern experimental techniques employing advanced detection set-ups was essential to reveal these exciting nuclear structure aspects in the actinide and transactinide regions since the production cross-section becomes extremely small with increasing mass and charge. Further technological progress, in particular, high intensity stable ion beam accelerator facilities presently under construction, as well as potentially in the farther future radioactive neutron rich ion beams provide a high discovery potential for the basic understanding of nuclear matter.

Colloquium : Superheavy elements: Oganesson and beyond

“…Nuclear structure observables strongly depend on the underlying shell structure. Unfortunately, current empirical shell model potentials as well as self-consistent DFT models do not produce robust, consistent explanations of the steadily-growing body of spectroscopic information on transactinides (Ackermann, 2015;Ackermann and Theisen, 2017;Gates et al, 2015;Herzberg, 2016;Rudolph et al, 2015Rudolph et al, , 2013Theisen et al, 2015).…”

“…To constrain nuclear models in the superheavy region, new high-quality data on bulk properties and spectroscopy of superheavy systems are required. High-quality experimental data have been accumulated on global properties of superheavy nuclei and their spectroscopy (Ackermann, 2015;Ackermann and Theisen, 2017;Herzberg, 2016;Rudolph et al, 2015Rudolph et al, , 2013Theisen et al, 2015).…”

“…The dedicated facilities in Dubna (Dmitriev et al, 2016) and RIKEN (Haba, 2016) will substantially increase the production of superheavy species for physics and chemistry. Other major players in different areas of superheavy nuclei research include GSI/FAIR in Germany (Münzenberg, 2015;Münzenberg et al, 2017), ORNL (Roberto et al, 2015;Roberto and Rykaczewski, 2018) and Berkeley (Gates, 2016;Gates et al, 2015Gates et al, , 2018 in the USA, GANIL in France (Ackermann and Theisen, 2017;Theisen, 2017), and several other major laboratories worldwide (Back, 2017;Hinde et al, 2017;Yang et al, 2013;…”

Impact of the surface energy coefficient on the deformation properties of atomic nuclei as predicted by Skyrme energy density functionals

“…(14), becomes larger than one. In fact, fissility is an often used criterion to define the so-called superheavy elements as those that have a vanishing liquid-drop fission barrier and only exist because the quickly fluctuating shell effects still generate a fission barrier [67]. Figure 8 shows the line of fissility x = 1 in the region of known transactinide nuclei, calculated by inserting the INM parameters as listed in Table I and the HF values for the surface and surface symmetry energy coefficients from Table II in Eq.…”

Production cross section and decay study of Es243 and Md249

“…Determining the boundaries of the nuclear chart, particularly in the region of super-heavy nuclei (SHN), is one of the key questions driving fundamental nuclear physics. The SHN owe their existence to shell effects as without them the Coulomb repulsion would make the nuclei beyond Z = 104 unstable against fission [1]. In this context, detailed spectroscopy of very heavy nuclei (VHN) and SHN is of paramount importance to provide information on the nuclear landscape close to the high-A limit of the nuclear chart, as well as on the nature of the predicted island of stability.…”