  The 64-Zn(t,3-He) reaction has been studied using a secondary triton beam of
115 MeV/nucleon to extract the Gamow-Teller transition-strength distribution to
64-Cu. The results were compared with shell-model calculations using the
pf-shell effective interactions KB3G and GXPF1A and with existing data from the
64-Zn(d,2-He) reaction. Whereas the experimental results exhibited good
consistency, neither of the theoretical predictions managed to reproduce the
data. The implications for electron-capture rates during late stellar evolution
were investigated. The rates based on the theoretical strength distributions
are lower by factors of 3.5-5 compared to the rates based on experimental
strength distributions.
