Visualizing coherent molecular rotation in a gaseous medium

TL;DR

This paper proposes a non-intrusive optical method using ultrashort circularly polarized laser pulses and a vortex wave plate to visualize and determine the instantaneous orientation of molecular rotation in gaseous media, aiding real-time analysis.

Contribution

It introduces a novel optical scheme for visualizing molecular rotational dynamics in gases, capable of handling complex molecular structures without intrusively perturbing the system.

Findings

Method successfully visualizes molecular orientation in simulations.

Applicable to both symmetric and asymmetric top molecules.

Potential for real-time, non-intrusive molecular dynamics monitoring.

Abstract

Inducing and controlling the ultrafast molecular rotational dynamics using shaped laser fields is essential in numerous applications. Several approaches exist that allow following the coherent molecular motion in real-time, including Coulomb explosion-based techniques and recovering molecular orientation from the angular distribution of high harmonics. We theoretically consider a non-intrusive optical scheme for visualizing the rotational dynamics in an anisotropic molecular gas. The proposed method allows determining the instantaneous orientation of the principal optical axes of the gas. The method is based on probing the sample using ultra-short circularly polarized laser pulses and recording the transmission image through a vortex wave plate. We consider two example excitations: molecular alignment induced by an intense linearly polarized laser pulse and unidirectional molecular rotation induced by a polarization-shaped pulse. The proposed optical method is promising for visualizing the dynamics of complex symmetric- and asymmetric-top molecules.