The production of about half of the heavy elements found in nature is assigned to a specific astrophysical nucleosynthesis process: the rapid neutron capture process (r-process). Although this idea has been postulated more than six decades ago, the full understanding faces two types of uncertainties/open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experimental information is available, and one has to rely strongly on theoretical predictions for nuclear properties. (b) While for many years the occurrence of the r-process has been associated with supernovae, more recent studies have cast substantial doubts on this environment. Alternative scenarios include the mergers of neutron stars, neutron-star black hole mergers, but possibly also rare classes of supernovae as well as hypernovae/collapsars with polar jet ejecta and also accretion disk outflows related to the collapse of fast rotating massive stars with high magnetic fields. Stellar r-process abundance observations, have provided insights into, and constraints on the frequency of and conditions in the responsible stellar production sites. One of them, neutron star mergers, was just identified and related to the Gravitational Wave event GW170817. High resolution observations, increasingly more precise due to improved experimental atomic data, have been particularly important in defining the heavy element abundance patterns of the old halo stars, and thus determining the extent, and nature, of the earliest nucleosynthesis in our Galaxy. Combining new results and important breakthroughs in the related nuclear, atomic and astronomical fields of science, this review attempts to provide an answer to the question "How Were the Elements from Iron to Uranium Made?" (Abridged)

Origin of the heaviest elements: The rapid neutron-capture process

Experiments with intense secondary beams of radioactive ions

The half-lives against \ensuremath{\alpha} decay of transuranium nuclei including superheavies are calculated by three methods: a semiempirical formula taking into account the magic numbers of nucleons, the analytical superasymmetric fission model, and the universal curves. The calculations based on $Q$ values determined by using the recently published compilations of atomic masses are compared to the experimental results.

α-decay half-lives of superheavy nuclei

▪ Abstract The proton drip-line defines the limit at which nuclei become unbound to the emission of a proton from their ground states. Low-Z nuclei lying beyond this limit only exist as short-lived resonances and cannot be detected directly. The location of the drip-line constrains the path of nucleosynthesis in explosive astrophysical scenarios such as novae and X-ray bursters, and consequently controls the rate of energy generation. In higher-Z regions of the drip-line, the potential energy barrier resulting from the mutual electrostatic interaction between the unbound proton and the core can cause nuclei to survive long enough to be detected. This review describes the recent major advances in the study of these exotic nuclei. Particular emphasis is placed on understanding the phenomenon of proton radioactivity and the unique insights it offers into the structure of nuclei lying beyond one of nature's fundamental limits to stability.

Nuclei beyond the proton drip-line

L. Westgaard

Papers

Target Techniques for the isolde on-line isotope separator

New techniques at ISOLDE-2

Short-lived isotopes of alkali and alkaline-earth elements studied by on-line isotope separator techniques

High-temperature carbide targets for fast on-line mass separation of alkali and noble gas elements

Widths for s- and d-wave α-decay of neutron-deficient isotopes with Z ≦ 82