Molecular spinning by a chiral train of short laser pulses

TL;DR

This paper presents a theoretical study of how a sequence of rotating polarized laser pulses can induce and control the direction of molecular rotation, enabling selective excitation of isotopologues and nuclear spin isomers.

Contribution

It introduces a novel chiral pulse train technique for controlling molecular rotation directionality and selectivity based on quantum interference effects.

Findings

Directionality of molecular rotation is achieved through quantum interference.

The method can selectively excite isotopologues and nuclear spin isomers.

Theoretical analysis demonstrated with nitrogen isotopologues and spin isomers.

Abstract

We provide a detailed theoretical analysis of molecular rotational excitation by a chiral pulse train -- a sequence of linearly polarised pulses with the polarisation direction rotating from pulse to pulse by a controllable angle. Molecular rotation with a preferential rotational sense (clockwise or counter-clockwise) can be excited by this scheme. We show that the directionality of the rotation is caused by quantum interference of different excitation pathways. The chiral pulse train is capable of selective excitation of molecular isotopologues and nuclear spin isomers in a mixture. We demonstrate this using 14N2 and 15N2 as examples for isotopologues, and para- and ortho-nitrogen as examples for nuclear spin isomers.