CHAOS ASSISTED TUNNELING AND NONSPREADING WAVE-PACKETS

Consider an initial state lying on a primary resonance island. The sta te may tunnel into the chaotic sea surrounding it and further escape t o infinity via chaotic diffusion. Properties of transport in such a si tuation are studied on an exemplary system - the hydrogen atom driven by microwaves. We show that the combination of tunneling followed by c haotic diffusion leads to peculiar large scale fluctuations of the AC Stark shift and ionization rates. An appropriate random matrix model d escribes accurately these statistical properties.