For D = 0, the curves in Fig. (a)-(c) coincide with the plane-wave ezDyson calculations in Fig. (a), while those in Fig. )-(f) with their counterparts in Fig. ). This is expected: with the dipole moment set to zero both types of calculations amount to the free-particle treatment of the detached electron. As D is increased, the curves calculated using eqn ( )-( ) deviate from the free-particle limit.