Isovector 0/sup +/. -->. 0/sup -/ transition observed in the reaction /sup 16/O(p,n)/sup 16/F

The angular distribution for the reaction /sup 16/O(p,n)/sup 16/F(0/sup -/) has been measured at E/sub p/ = 35 MeV between 0/sup 0/ and 140/sup 0/ (lab), or momentum transfer 0.34--2.0 fm/sup -1/. This is the first observation of an isovector 0/sup +/..-->..0/sup -/ transition, corresponding to a pure longitudinal spin response, at large momentum transfers. Distorted-wave Born-approximation calculations with the M3Y interaction give a reasonable account of the observed cross sections except at 1.4< or approx. =q< or approx. =2.0 fm/sup -1/. This discrepancy might be due to the effects of the pion field in nuclei.