We extend the procedure originally suggested by Dalgarno and Lewis in studying the second-order Stark effect for the ground-state hydrogen atom to the excited states. We solve the perturbation equations for the excited states of hydrogen atom placed in an external electric field to obtain expressions for the perturbed wavefunctions. Here the emphasis is on studying in detail the nature of the perturbed wavefunction rather than energy shifts as investigated in most of the attempts made so far. The effect of the electric field on these wavefunctions is analysed and the values of the electric polarizability of the hydrogen atom in the excited states obtained in this way are compared with the earlier work.
The excited states structure for chloroethylene under the external electric field
