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

Abstract

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 utilised or be detrimental.

GRAPHICAL ABSTRACT

Keywords:

• Kicked rotors
• orientation and alignment
• quantum control

Acknowledgments

We thank Gerard Meijer for his interest and support, and Marjan Mirahmadi and Jesús Pérez Ríos for fruitful discussions. MK acknowledges support by the IMPRS for Elementary Processes in Physical Chemistry. We dedicate this paper, with much admiration and our best wishes, to Jürgen Troe on the occasion of his grand jubilee. Among his many contributions to laser chemistry is his work on laser ablation where he made use of fixed fluence to understand the ablation rate at varying pulse lengths [73].

Disclosure statement

No potential conflict of interest was reported by the author(s).