  The 51Cr neutrino source experiments play a unique role in testing overall
operations of the GALLEX and SAGE solar neutrino experiments. Recently Hata and
Haxton argued that the excited-state contribution to the 71Ga cross section for
51Cr neutrino absorption might not be known reliably, despite forward-angle
(p,n) measurements. A large-basis shell model calculation reported here
indicates that the unusual situation they envisioned - destructive interference
between weak spin and strong spin-tensor amplitudes - does occur for the
transition to the first excited state in 71Ge. The calculation provides a
counterexample to procedures previously used to determine the 51Cr cross
section: the predicted (p,n) cross section for this state agrees with
experiment, while the BGT value is well outside the accepted
3-standard-deviation limit. The results argue for a shift in the interpretation
of the source experiments: they become more crucial as measurements of the 71Ga
detector response to 7Be solar neutrinos, and less definitive as wholly
independent tests of 71Ge recovery and counting efficiencies.
