Semiclassical Calculation of Transition Matrix Elements for Atoms in External Fields

Closed orbit theory is generalized to the semiclassical calculation of cross-correlated recurrence functions for atoms in external fields. The cross-correlation functions are inverted by a high resolution spectral analyzer to obtain the semiclassical eigenenergies and transition matrix elements. The method is demonstrated for dipole transitions of the hydrogen atom in a magnetic field. This is the first semiclassical calculation of individual quantum transition strengths from closed orbit theory.