Electron-nuclear correlated multiphoton-route to Rydberg fragments of molecules

Wenbin Zhang,Qinying Ji,Kang Lin,Xiaochun Gong,Jian Wu,Hui Li,Fenghao Sun,Feng He,Junjie Qiang,Peifen Lu,Hanxiao Li,Junyang Ma

doi:10.1038/s41467-019-08700-5

Abstract

Atoms and molecules exposed to strong laser fields can be excited to the Rydberg states with very high principal quantum numbers and large orbitals. It allows acceleration of neutral particles, generate near-threshold harmonics, and reveal multiphoton Rabi oscillations and rich photoelectron spectra. However, the physical mechanism of Rydberg state excitation in strong laser fields is yet a puzzle. Here, we identify the electron-nuclear correlated multiphoton excitation as the general mechanism by coincidently measuring all charged and neutral fragments ejected from a H2 molecule. Ruled by the ac-Stark effect, the internuclear separation for resonant multiphoton excitation varies with the laser intensity. It alters the photon energy partition between the ejected electrons and nuclei and thus leads to distinct kinetic energy spectra of the nuclear fragments. The electron-nuclear correlation offers an alternative visual angle to capture rich ultrafast processes of complex molecules.

Highlights

Atoms and molecules exposed to strong laser fields can be excited to the Rydberg states with very high principal quantum numbers and large orbitals
We measure the coincidence between the freed electron, charged and neutral nuclear fragments ejected from a H2 molecule and reveal a complete picture for the generation of Rydberg fragments in the strong-field breaking of molecules
H2 molecule exposed to a strong laser field may be doubly ionized and eventually break into two bare protons, that is, H2 → H+ + H+ + 2e, hereafter denoted as (H+, H+) channel

Summary

Introduction

Atoms and molecules exposed to strong laser fields can be excited to the Rydberg states with very high principal quantum numbers and large orbitals It allows acceleration of neutral particles, generate near-threshold harmonics, and reveal multiphoton Rabi oscillations and rich photoelectron spectra. Ruled by the ac-Stark effect, the internuclear separation for resonant multiphoton excitation varies with the laser intensity It alters the photon energy partition between the ejected electrons and nuclei and leads to distinct kinetic energy spectra of the nuclear fragments. Due to the ac-Stark shift of the potentials, the internuclear separation for resonant Rydberg state excitation increases with the laser intensity It alters the photon energy partition between the ejected electrons and nuclei and leads to distinct nuclear kinetic energy spectra of the Rydberg fragmentation channel, which explains the experimental observations driven by different laser intensities and wavelengths

Methods

Results

Conclusion