  Charged pion photoproduction is proposed as a new method to study halo
nuclei. In particular, it is demonstrated that the reaction
17O(gamma,pi^-)17F(1/2+, 0.495 MeV) is well-suited to investigate the
well-known proton halo in 17F which is not amenable to radioactive beam
experiments. The cross sections are shown to be very sensitive to the halo
structure of the loosely bound proton.
