2 PITCHFORK BIFURCATIONS IN THE POLAR QUADRATIC ZEEMAN-STARK EFFECT

In the framework of classical mechanics, a study of the hydrogen atom in the presence of parallel electric and magnetic fields is presented when the magnetic quantum number m is zero. By means of perturbation m ethods and Poincare surfaces of section, the existence of the three st ates experimentally detected by Cacciani et al. (the so-called I, II, and III Cacciani's states), their energy extensions, their evolution a nd their disappearance are explained as a result of two pitchfork bifu rcations. (C) 1998 Elsevier Science B.V.