Nuclei beyond the proton drip-line

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.