Quantum dynamics of a polar rotor acted upon by an electric rectangular pulse of variable duration

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