Enhanced Excited State Population and Coherence via Adiabatic Tunneling Ionization and Excitation

TL;DR

This paper introduces an adiabatic approach to enhance and control excited state populations and coherence in ionic systems using intense laser pulses, revealing new ultrafast phenomena and potential applications in chemistry and lasing.

Contribution

It develops a semi-analytical adiabatic model for tunneling and excitation, uncovering novel sub-cycle processes and significantly boosting excited state populations and coherence.

Findings

Excited state population can be increased by an order of magnitude.

Coherence amplitude can be boosted by over four orders of magnitude.

The model predicts different behaviors for single-cycle versus multi-cycle pulses.

Abstract

Tunneling ionization followed by strong-field excitation leads to important ultrafast phenomena such as charge migration and lasing. Recent theoretical developments suggest that the population of the ionic excited state can be greatly enhanced due to the complex interplay between tunneling and excitation. In this Letter, using an adiabatic approach for both tunneling and excitation, semi-analytical solutions are derived for the population and coherence of a two-level ionic system. This approach removes the strong-field dressing, revealing novel sub-half-cycle processes for excited state population and coherence buildup. It predicts that the excited state population is enhanced by an order of magnitude, independent of the laser wavelength, while coherence amplitude can be boosted by over four orders of magnitude for a multi-cycle pulse. For a single-cycle pulse, it suggests that coherence amplitude decreases rapidly as the wavelength increases. This work introduces a novel framework for generating and controlling the electronic excited state and coherence using intense laser pulses, with applications in strong-field control of chemistry and lasing.