Nuclei Beyond the Proton Drip-Line

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.

Proton emission half-lives within a Gamow-like model

“…Our HFB calculations with the Gogny force predict that 131 Eu is well deformed in its ground state (Q 2 = 7 b), which can significantly decrease the proton emission half-life with respect to our estimate obtained in the model made for spherical and nearly spherical nuclei. The results, given in brackets in table 1, suggest that the main reason for the discrepancies is the value of the angular momentum used in the analysis, which is not directly measured in experiment, but deduced from the comparison of the measured proton energies and the spectroscopic factors with theoretical estimates [3,32]. A similar discussion to that based on figs.…”

Decay rate of triaxially deformed proton emitters

“…The fundamental simplicity of the proton decay process in nuclides whose ground states are unstable to proton emission has enabled a good deal of nuclear structure information to be obtained on nuclei beyond the proton drip line [1]. The observable quantities are the proton energies and half-lives.…”

γ-ray spectroscopy of the odd-oddN=Z+2deformed proton emitter112Cs

“…This interest has been motivated by calculations which suggest that structural properties may change significantly with a severe imbalance of neutrons and protons, compared to stable isotopes [1]. In the A = 110 region, the locus of nuclei having N = Z and the proton drip-line lie in very close proximity to each other.…”