  Electron capture rates on neutron-rich nuclei (A>65) were calculated within
the Random Phase Approximation with partial number formalism, including allowed
and forbidden transitions. The partial occupation numbers were provided as a
function of temperature by Shell-Model Monte Carlo calculations, including an
pairing+quadrupole interaction. Capture rates on relevent nuclei were
calculated for density and temperature conditions during the core collapse of a
massive star. It was found that electron captures on nuclei can compete with
electron captures on free protons. Furthermore, they produce neutrinos with
average energies lower than neutrinos emitted from captures on free protons,
with possible consequences on the cooling of the core.
