To follow or not to follow
According to Newton's second law of classical mechanics, an object
responds to an external force by changing its momentum.
This principle is also often used to explain quantum
mechanical phenomena. For example, the generation of high harmonics radiation and
attosecond pulses can be understood in terms of the classical motion
of an electron in the laser field. The situation changes, if the electron is located inside a
molecule, as our numerical simulations for a dissociating hydrogen
molecular ion in an ultrashort intense laser pulse show. Here, the
momentum distribution of the electron is not only shifted by the
external laser field, but also modulated by an interference effect due
to the two nuclei. The Figure shows this modulation for different intensities
(columns) and time instants during the dissociation (rows).
The net electronic probability current,
that corresponds to the classical motion of the electron,
can follow or oppose to the laser electric force,
depending on the laser intensity. Our results may be relevant for the control of chemical
reaction dynamics with light.
F. He et al., Phys. Rev. Lett. 101 (2008) 213002
Collaboration: F. He and U. Thumm (Kansas State University, USA)
