THE EFFECT OF ATOMIC POLARIZABILITY IN ELECTRON-HYDROGEN EXCITATION

In the perturbation series treatment of scattering, the effect of atom ic polarizability first appears in the second-order term. Consequently , the atomic polarizability does not contribute to the scattering ampl itudes in the usual first-order distorted-wave treatment without makin g approximations. However, it is known that this effect is important a nd including it in a first-order treatment is desirable. This paper in vestigates different methods for including the effect of polarizing th e target atom in a first-order treatment for electron-hydrogen scatter ing. In particular, we examine approximations for including the effect of atomic polarizability on the projectile wavefunction as well as th e effect of distortion of the atomic wavefunction. For the latter case , we approximate the polarized atomic states as Stark states, and have used these states for both the determination of the final-state poten tial and the evaluation of matrix elements. The accuracy of the variou s methods is ascertained by comparing their results with those obtaine d from a second-order distorted-wave Born approximation using the red part of the Green's function. The results also are compared with avail able experimental data for electron-hydrogen scattering.