  We study the impact of neutrino-pair production from the de-excitation of
highly excited heavy nuclei on core-collapse supernova simulations, following
the evolution up to several 100 ms after core bounce. Our study is based on the
AGILE-Boltztran supernova code, which features general relativistic radiation
hydrodynamics and accurate three-flavor Boltzmann neutrino transport in
spherical symmetry. In our simulations the nuclear de-excitation process is
described in two different ways. At first we follow the approach proposed by
Fuller and Meyer [Astrophys. J. 376,701 (1991)], which is based on strength
functions derived in the framework of the nuclear Fermi-gas model of
non-interacting nucleons. Secondly, we parametrize the allowed and forbidden
strength distributions in accordance with measurements for selected nuclear
ground states. We determine the de-excitation strength by applying the Brink
hypothesis and detailed balance. For both approaches, we find that nuclear
de-excitation has no effect on the supernova dynamics. However, we find that
nuclear de-excitation is the leading source for the production of electron
antineutrinos as well as heavy-lepton flavor (anti)neutrinos during the
collapse phase. At sufficiently high densities, the associated neutrino spectra
are influenced by interactions with the surrounding matter, making proper
simulations of neutrino transport important for the determination of the
neutrino-energy loss rate. We find that even including nuclear de-excitations,
the energy loss during the collapse phase is overwhelmingly dominated by
electron neutrinos produced by electron captures.
