A process that is one of the ways in which nucleosynthesis occurs in stars, with ‘p’ standing for proton. In the p-process protons are added to nuclei, thereby changing each nucleus to a nucleus that has an atomic number one higher than the original. Nuclei formed in this way are proton-rich, it being impossible to make such nuclei by capturing neutrons. The p-process is not efficient as there is a strong Coulomb barrier (see potential barrier) between a proton and a nucleus, with this barrier requiring high energies or temperatures to be overcome. See also r-process; s-process.