Stark mixing of degenerate states

The initial value problem and the field dressing associated with the time-dependent Stark effect are treated, which are of importance in applications. An exact solution of time-dependent field mixing of degenerate states as an initial value problem is obtained in the restricted subspace of a given principal quantum number of hydrogenic ions, with the field-dependent phases explicitly included. The field mixing in terms of the transformation from spherical to parabolic representation is clarified. The distinction between these two problems is stressed and previous work on the field-perturbed dielectronic recombination is re-examined.