Sub-cycle coherent control of ionic dynamics via transient ionization injection

Qian Zhang,Zhiming Chen,Ya Cheng,Hongqiang Xie,Jinping Yao,Jing Zhao,Xiaowei Wang,Hongbin Lei,Guihua Li,Zengxiu Zhao

doi:10.1038/s42005-020-0321-7

Abstract

Ultrafast ionization of atoms or molecules by intense laser pulses creates extremely non-stationary ionic states. This process triggers attosecond correlated electron-hole dynamics and subsequent ultrafast non-equilibrium evolution of matters. Here we investigate the interwoven dynamic evolutions of neutral nitrogen molecules together with nitrogen ions created through transient tunnel ionization in an intense laser field. Based on the proposed theoretical frame, it is found that nitrogen molecular ions are primarily populated in the electronically excited states, rather than staying in the ground state as predicted by the well-known tunneling theory. The unexpected result is attributed to sub-cycle switch-on of time-dependent polarization by transient ionization and dynamic Stark shift mediated near-resonant multiphoton transitions. These findings corroborate the mechanism of nitrogen molecular ion lasing and are likely to be universal. The present work opens a route to explore the important role of transient ionization injection in strong-field induced non-equilibrium dynamics.

Highlights

Ultrafast ionization of atoms or molecules by intense laser pulses creates extremely nonstationary ionic states
The temporal confined strong field ionization (SFI) creates broad bandwidth non-stationary ionic states along with the launching of attosecond electron wavepacket forming the foundation of attosecond physics[4,5,6,7,8]
Recent experiments indicate that the interplay of sub-cycle SFI and the followed ion-laser coupling is indispensable for nitrogen molecular ion lasing[12,13,14,15,16], which suggests the new possibility to manipulate the ion coherence upon its creation toward ion-based quantum optics

Summary

Introduction

Ultrafast ionization of atoms or molecules by intense laser pulses creates extremely nonstationary ionic states. Ionization creates the ion in three possible electronic states at the moment ti by releasing the electron, the remaining linearly polarized laser field will further induce coherence and population transfer among the electronic and vibrational states with the couplings depending on the geometry of the molecular ion.

Results

Conclusion