Particle radioactivity of exotic nuclei

For the atomic nuclei located beyond the drip-lines, new forms of radioactivity are possible due to the instability against the emission of particles. At the neutron-deficient limit, single-proton and two-proton radioactivity are characteristic phenomena. While the former is well understood and represents a mature research field of nuclear spectroscopy, the knowledge about the latter is still scarce but growing rapidly. In some areas of the proton drip-line, α decay sets in as the main decay mode. This paper briefly describes the phenomena of particle emission at the proton drip-line and presents some examples illustrating the current status of experimental achievements and the theoretical understanding. The idea of the Gamow state as a unifying concept in the description of particle radioactivity is highlighted. The possibility for neutron radioactivity is briefly discussed.