Feynman's path-integral approach for intense-laser-atom interactions

Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these h ighly nonlinear processes can be found in terms of a generalization of clas sical Newtonian particle trajectories, the so-called quantum orbits. Very f ew quantum orbits are necessary to reproduce the experimental results. Thes e orbits are clearly identified, thus opening the way for an efficient cont rol as well as previously unknown applications of these processes.