Semiclassical calculation of transition matrix elements for atoms in external fields

Closed-orbit theory is generalized to the semiclassical calculation of cros s-correlated recurrence functions for atoms in external fields. The cross-c orrelation 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 ma gnetic field. This is an alternative semiclassical calculation of individua l quantum transition Strengths from closed-orbit theory. [S1050-2947(99)511 04-9].