Table of contents

The results on the synthesis of new superheavy elements, synthesized in complete fusion reactions of ⁴⁸Ca ions with actinide targets, are summarized and analyzed. The perspectives for the synthesis of element 117, as well as of elements with Z⩾118 are also considered.

Nuclear reactions leading to formation of new superheavy elements and isotopes are discussed. The scope and limitations of different nuclear reactions ("cold" and "hot" synthesis, fusion of fission fragments, transfer reactions and reactions with radioactive ion beams) are analyzed, trying to find most promising reactions which may be used at available facilities.

Theoretical descriptions of superheavy atomic nuclei are shortly reviewed and illustrated by their results. Such properties of these nuclei as their shapes, masses, fission barriers, decay modes, decay energies, half-lives, are discussed. Special attention is given to the shell structure of the nuclei, due to which they exist. The role of the physical studies of the superheavy nuclei for the chemical research on the superheavy elements and, more generally, the relationship between these two kinds of investigation is underlined. This stresses the importance of close cooperation between physicists and chemists, experimentalists and theoreticians, in these studies.

The nuclear shell model predicts that the next doubly magic shell-closure beyond ²⁰⁸Pb is at the proton number Z=114, 120, or 126 and at the neutron number N=172 or 184. The outstanding aim of experimental investigations is the exploration of this region of spherical 'Super Heavy Elements' (SHEs). Using cold fusion reactions which are based on lead and bismuth targets, the new elements from 107 to 112 were synthesized at GSI in Darmstadt, Germany. Some of these results were confirmed at RIKEN in Wako, Japan, where also a relatively neutron-deficient isotope of element 113 was synthesized. In hot fusion reactions of ⁴⁸Ca projectiles with actinide targets, a more neutron-rich isotope of element 112 and the new elements from 113 to 116 and even 118 were produced at FLNR in Dubna, Russia. Recently, part of these hot fusion data, which represent the first identification of nuclei located on the predicted island of SHEs, were confirmed in two independent experiments. The decay data reveal that for the heaviest elements, the dominant decay mode is α emission rather than fission. The decay properties as well as reaction cross-sections are compared with results of theoretical studies.

The review briefly considers the problems of synthesis and chemical identification of superheavy elements. The specific features of their properties are determined by the relativistic effects. The synthesis and chemical investigations into bohrium and element 112 are discussed as examples.

This paper highlights some of the current basic nuclear physics research at Lawrence Livermore National Laboratory (LLNL). The work at LLNL concentrates on investigating nuclei at the extremes. The Experimental Nuclear Physics Group performs research to improve our understanding of nuclei, nuclear reactions, nuclear decay processes and nuclear astrophysics; an expertise utilized for important laboratory national security programs and for world-class peer-reviewed basic research.

Relativistic electronic structure calculations of superheavy elements (Z⩾104) are analyzed. Preference is given to those related to experimental research. The role of relativistic effects is discussed.

Relativistic pseudopotential approach to the electronic structure simulation of superheavy elements (SHE) compounds is presented. Advanced formulations of this approach leaving both valence and outer-core electronic shells for explicit treatment give rise to simple and efficient computational techniques ensuring highly accurate description of most chemical properties of SHE. At present, the errors due to the use of approximate methods for solving the correlation problem for a subsystem of valence electrons are much larger than those stemming from the pseudopotential approximation itself. Recent applications to the studies of the chemistry of elements 112 (eka-Hg) and 114 (eka-Pb) are reviewed; properties of these elements and their lighter homologues, Hg and Pb, are compared.