Few-body systems

F. Gabern, W. S. Koon, J. E. Marsden, S. D. Ross, and T. Yanao, Application of tube dynamics to non-statistical reaction processes, Few-Body Systems 38, 167 (2006). 

Quasi-Bound States of Electronic and Positronic Few-Body Systems... 

E. Braaten, H.-W. Hammer, Universality in few-body systems with large scattering length, Phys. Rep. 428 (2006) 259. 

It is clear that a core-hole represents a very interesting example of an unstable state in the continuum. It is, however, also rather complicated [150]. A simpler system with similar characteristics is a doubly excited state in few-body systems, as helium. Here, it is possible [151-153] to simulate the whole sequence of events that take place when the interaction with a short light pulse first creates a wave packet in the continuum, including doubly excited states, and the metastable components subsequently decay on a timescale that is comparable to the characteristic time evolution of the electronic wave packet itself. On the experimental side, techniques for such studies are emerging. Mauritsson et al. [154] studied recently the time evolution of a bound wave packet in He, created by an ultra-short (350 as) pulse and monitored by an IR probe pulse, and Gilbertson et al. [155] demonstrated that they could monitor and control helium autoionization. Below, we describe how a simulation of a possible pump-probe experiment, targeting resonance states in helium, can be made. 

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