By using several optical potentials which fit satisfactorily results of a recent experiment on the elastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ by ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at $E_{\mathrm{lab}}=55\mathrm{}$ MeV, exact calculations were performed so as to locate the positions of the Regge poles, and to evaluate the associated residues and corresponding background integrals. Based on the results thus obtained, a discussion is given of the roles which the pole and background terms play in the description of the scattering between two heavy ions.

NUCLEAR REACTIONS Exact derivation of Regge poles; Residue; Pole and background decomposition of scattering amplitude; ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+ ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at $E_{\mathrm{lab}}=55\mathrm{}$ MeV.

• Received 10 February 1978

DOI:https://doi.org/10.1103/PhysRevC.18.1282