Classical trajectories of molecules exposed to few-optical-cycle light pulses

It is shown that, in the framework of classical electrodynamics and in some peculiar cases, an exhaustive description of rotational evolution of molecules driven by intense few-optical-cycle laser pulses should consider the electric field of the pulse rather than its intesity envelope. We show that, at moderate pulse intensities, nonlinear effects driven by the molecular hyperpolarizability play a significant role. These findings are illustrated by numerical simulations concerning the classical motion of several molecules exposed to few-cycle light pulses.