Probing multiphoton light-induced molecular potentials

M Kübel,P B Corkum,D M Villeneuve,A D Bandrauk,A Staudte,Z Dube,M J J Vrakking,A Yu Naumov,S Chelkowski,M Spanner

doi:10.1038/s41467-020-16422-2

Abstract

The strong coupling between intense laser fields and valence electrons in molecules causes distortions of the potential energy hypersurfaces which determine the motion of the nuclei and influence possible reaction pathways. The coupling strength varies with the angle between the light electric field and valence orbital, and thereby adds another dimension to the effective molecular potential energy surface, leading to the emergence of light-induced conical intersections. Here, we demonstrate that multiphoton couplings can give rise to complex light-induced potential energy surfaces that govern molecular behavior. In the laser-induced dissociation of H2+, the simplest of molecules, we measure a strongly modulated angular distribution of protons which has escaped prior observation. Using two-color Floquet theory, we show that the modulations result from ultrafast dynamics on light-induced molecular potentials. These potentials are shaped by the amplitude, duration and phase of the dressing fields, allowing for manipulating the dissociation dynamics of small molecules.

Highlights

The strong coupling between intense laser fields and valence electrons in molecules causes distortions of the potential energy hypersurfaces which determine the motion of the nuclei and influence possible reaction pathways
While light-induced conical intersections (LICI) are a consequence of single-photon couplings and the potential energy scales linearly with respect to variations of the laser field strength, multiphoton couplings lead to unique structures of their own
The one-dimensional (1D) treatment of single and multiphoton resonances has led to the prediction of lightinduced potentials (LIPs)[23,24,25,26,27,28,29], and anomalous fragment angular distributions have been predicted in the non-perturbative regime[30]

Summary

Introduction

The strong coupling between intense laser fields and valence electrons in molecules causes distortions of the potential energy hypersurfaces which determine the motion of the nuclei and influence possible reaction pathways. The coupling strength varies with the angle between the light electric field and valence orbital, and thereby adds another dimension to the effective molecular potential energy surface, leading to the emergence of light-induced conical intersections. The single-photon transition between two dipole-coupled electronic states can create a conical, albeit transient, intersection These localized features of the laser-dressed potential energy surface have been dubbed light-induced conical intersections (LICI)[8,9]. Their precise position, and the underlying dipole coupling strength are determined by the frequency and intensity of the incident light. The consequences of the angle-dependent coupling strength around nonlinear point intersections for the dissociation dynamics have so far been largely unexplored

Methods

Results

Conclusion