ProtonenDripLinie

ProtonenDripLinie, or the proton drip line, is the boundary on the proton-rich side of the chart of nuclides beyond which nuclei cannot bind an additional proton. It is defined by the condition that the one-proton separation energy S_p becomes zero or negative, making proton emission energetically favorable. The line delineates the set of nuclides that are bound with respect to proton emission from those that are not. It is the proton-rich counterpart of the neutron drip line and is strongly influenced by the Coulomb repulsion between protons and by nuclear shell structure.

Locating the proton drip line relies on a combination of experimental measurements and theoretical models. Experimentally, the line is probed by mass measurements, direct observation of proton radioactivity, and production of proton-rich isotopes in fusion-evaporation or projectile fragmentation reactions. Mass properties and proton emission energies provide S_p values that map the boundary, although many regions remain uncharted due to short lifetimes and low production rates.

On the theory side, global mass models and energy-density functionals predict the position of the line. Influencing factors include shell closures, pairing correlations, deformation, and the escalating Coulomb barrier for proton-rich systems. The drip line shows irregularities tied to nuclear structure, so different models may disagree on the exact endpoint for a given element.

Relevance: The proton drip line is important for understanding nucleosynthesis in proton-rich environments, such as the rp-process in X-ray bursts, and for testing nuclear theories of binding and decay. Ongoing experimental and theoretical work aims to extend the known boundary to higher Z and more proton-rich isotopes.