Analytic expressions have been found for transition probabilities in a degenerate
n-level
atom interacting with a strong external field that gives a common time dependence
to all of the transition matrix elements. Except for solving a simple nth-order
equation to determine eigenvalues of dressed states, the method is entirely analytic.
These expressions may be used to control electron populations in degenerate
n-level atoms. Examples
are given for n = 2
and 3.