Evidence of nonlocality due to a gradient term in the optical model
  We demonstrate that the presence of a velocity-dependent term in the phenomenological optical potential simulates a source of nonlocality. This is achieved by showing that, in the interior of the nucleus, the nonlocal wave functions are different from the corresponding local ones obtained in the absence of the velocity-dependent term in accordance with the Perey effect. It is also shown that the enhancement or suppression of the nonlocal wave function is energy as well as angular momentum dependent. The latter is in line with the results of previous works that introduced parity dependent terms in the conventional optical potential. 
M. I. Jaghoub, G. H. Rawitscher
nucl-th