Threshold behavior of inelastic-scattering cross sections

The behavior of scattering cross sections near an excitation threshold is examined for the case of long-range potentials. The theory is confirmed by computations of e-Li scattering. Recent observations of threshold structure in e-Na collisions are ascribed to a D1 resonance of Na-. A true cusp should occur only in the P1 partial cross section. © 1973 The American Physical Society.