Because of the sheer number of electrons interacting with each other, it is not possible to solve exactly the problem of many - electron motion in solids using quantum mechanical theory. (sciencedaily.com)
So far, the influence of this interaction on the very fast electron motions following the absorption of light has remained unclear. (sciencedaily.com)
In those experiments, the resulting state was «photographed» with a longer infrared pulse, which itself had a significant influence on the ensuing electron motion. (sciencedaily.com)