  Observation of internal quantum dynamics relies on correlations between the
system being observed and the measurement apparatus. We propose using the
center-of-mass (c.m.) degrees of freedom of atoms and molecules as a "built-in"
monitoring device for observing their internal dynamics in non-perturbative
laser fields. We illustrate the idea on the simplest model system - the
hydrogen atom in an intense, tightly-focused infrared laser beam. To this end,
we develop a numerically-tractable, quantum-mechanical treatment of
correlations between internal and c.m. dynamics. We show that the transverse
momentum records the time excited states experience the field, allowing
femtosecond reconstruction of the strong-field excitation process. The ground
state becomes weak-field seeking, an unambiguous and long sought-for signature
of the Kramers-Henneberger regime.
