  Assuming that two incoming annihilating particles interact by a generally
massive attractive vector potential,we find, by taking the non-relativistic
limit of the field theory ladder diagrams, that the complete annihilation
amplitude A is equal to: the convolution of a solution of the Schroedinger
equation (including the vector potential) with the Fourier transform of the
bare (i.e. ignoring the attraction) annihilation amplitude A0. The main novelty
is that A0 is completely arbitrary. In particular for a massless vector
potential we find for the l-partial-wave cross-section the Sommerfeld
enhancement 2pi/(l!)^2 (alpha/ v)^{2l+1} (v relative velocity), e.g. for the P
wave the enhancement 2pi(alpha/ v)^3.
