The dynamics of the wave packet generated by a short-pulse laser can be characterized by an autocorrelation function. The autocorrelation function is an experimentally measurable quantity. This paper shows that the autocorrelation function can be written as a sum of modified Gaussian functions that correspond to the closed orbits of the system. The autocorrelation function can be calculated by using existing algorithms in closed-orbit theory. As an application of the theory, the autocorrelation function is obtained for a system that consists of an ${\mathrm{H}}^{\mathrm{-}}$ ion in a static electric field.

• Received 20 June 1994

DOI:https://doi.org/10.1103/PhysRevA.51.1955