Echoes in Unidirectionally Rotating Molecules

TL;DR

This paper reports the first experimental observation of molecular unidirectional rotation (UDR) echoes induced by twisted polarization laser pulses, analyzed through classical and quantum models, revealing new insights into molecular rotation dynamics.

Contribution

It introduces the experimental observation of UDR echoes and demonstrates their analysis using classical and quantum simulations, highlighting their potential for studying molecular relaxation.

Findings

UDR echoes are observed experimentally using twisted polarization pulses.

The rotation sense of echoes is controlled by the second pulse's twisting direction.

Classical and quantum models accurately reproduce the experimental results.

Abstract

Abstract We report the experimental observation of molecular unidirectional rotation (UDR) echoes, and analyze their origin and behavior both classically and quantum mechanically. The molecules are excited by two time-delayed polarization-twisted ultrashort laser pulses and the echoes are measured by exploding the molecules and reconstructing their spatial orientation from the detected recoil ions momenta. Unlike alignment echoes which are induced by linearly polarized pulses, here the axial symmetry is broken by the twisted polarization, giving rise to molecular unidirectional rotation. We find that the rotation sense of the echo is governed by the twisting sense of the second pulse even when its intensity is much weaker than the intensity of the first pulse. In our theoretical study, we rely on classical phase space analysis and on three-dimensional quantum simulations of the laser-driven molecular dynamics. Both approaches nicely reproduce the experimental results. Echoes in general, and the unique UDR echoes in particular, provide new tools for studies of relaxation processes in dense molecular gases.