Semiclassical photoionization cross section of the hydrogen atom in a magnetic field - art. no. 062704

We rest the accuracy of the semiclassical approximation for a completely ch aotic system, the strongly magnetized hydrogen atom. We study a quantity of direct experimental interest, the photoabsorption cross section. The stand ard semiclassical approximation using periodic orbits is used (without any additional trick to improve convergence) and is shown to agree very well wi th a fully resolved ab initio quantum "exact" calculation. We also study th e families of periodic orbits giving the dominant contributions to the spec trum.