Visualizing molecular unidirectional rotation

TL;DR

This paper presents the first experimental visualization of the time-dependent evolution of unidirectional molecular rotation using Coulomb explosion imaging, revealing detailed quantum revival phenomena and confirming numerical simulations.

Contribution

It introduces a novel experimental method to visualize the evolution of unidirectional molecular rotation, filling a key gap in understanding molecular rotational dynamics.

Findings

Visualization of the rotational wave packet evolution

Observation of quantum revival and unidirectional rotation

Agreement between experimental results and simulations

Abstract

A molecule can be optically accelerated to rotate unidirectionally at a frequency of a few terahertzes which is many orders higher than the classical mechanical rotor. Such a photon-induced ultrafast molecular unidirectional rotation has been well explored as a controllable spin of the molecular nuclear wave packet. Although it has been observed for more than 10 years, a complete imaging of the unidirectional rotating nuclear wave packet is still missing, which is essentially the cornerstone of all the exploring applications. Here, for the first time, we experimentally visualize the time-dependent evolution of the double-pulse excited molecular unidirectional rotation by Coulomb explosion imaging the rotational nuclear wave packet. Our results reveal comprehensive details undiscovered in pioneering measurements, which exhibits as a joint of the quantum revival of the impulsively aligned rotational wave packet and its unidirectional rotation following the angular momentum conservation. The numerical simulations well reproduce the experimental observations and intuitively revivify the thoroughgoing evolution of the rotational wave packet.