We explore neutrino capture during $r$-process nucleosynthesis in neutrino-driven ejecta from nascent neutron stars. We focus on the interplay between charged-current weak interactions and element synthesis, and we delineate the important role of equilibrium nuclear dynamics. During the period of coexistence of free nucleons and light and/or heavy nuclei, electron neutrino capture inhibits the $r$-process. At all stages, capture on free neutrons has a larger impact than capture on nuclei. However, neutrino capture on heavy nuclei by itself, if it is very strong, is also detrimental to the $r$-process until large nuclear equilibrium clusters break down and the classical neutron-capture phase of the $r$-process begins. The sensitivity of the $r$-process to neutrino irradiation means that neutrino-capture effects can strongly constrain the $r$-process site, neutrino physics, or both. These results apply also to $r$-process scenarios other than the neutrino-heated winds.

• Received 28 April 1998

DOI:https://doi.org/10.1103/PhysRevC.58.3696