  As demonstrated in our previous work [J. Chem. Phys. 149, 174109 (2018)], the
kinetic energy imparted to a quantum rotor by a non-resonant electromagnetic
pulse with a Gaussian temporal profile exhibits quasi-periodic drops as a
function of the pulse duration. Herein, we show that this behaviour can be
reproduced with a simple waveform, namely a rectangular electric pulse of
variable duration, and examine, both numerically and analytically, its causes.
Our analysis reveals that the drops result from the oscillating populations
that make up the wavepacket created by the pulse and that they are necessarily
accompanied by drops in the orientation and by a restoration of the pre-pulse
alignment of the rotor. Handy analytic formulae are derived that allow to
predict the pulse durations leading to diminished kinetic energy transfer and
orientation. Experimental scenarios are discussed where the phenomenon could be
utilized or be detrimental.
