  We propose a new model to calculate stellar electron capture rates for
neutron-rich nuclei. These nuclei are encountered in the core-collapse of a
massive star. Using the Shell Model Monte Carlo approach, we first calculate
the finite temperature occupation numbers in the parent nucleus. We then use
these occupation numbers as a starting point for calculations using the random
phase approximation. Using the RPA approach, we calculate electron capture
rates including both allowed and forbidden transitions. Such a hybrid model is
particularly useful for nuclei with proton numbers Z<40 and neutron numbers
N>40, where allowed Gamow-Teller transitions are only possible due to
configuration mixing by the residual interaction and by thermal unblocking of
$pf$-shell single-particle states. Using the even germanium isotopes Ge-68 to
Ge-76 as examples, we demonstrate that the configuration mixing is strong
enough to unblock the Gamow-Teller transitions at all temperatures relevant to
core-collapse supernovae.

Nuclear Theory