Control of photodissociation with the dynamic Stark effect induced by THz pulses

A Tóth,G J Halász,Á Vibók,A Csehi

doi:10.1103/physrevresearch.2.013338

Abstract

We demonstrate how dynamic Stark control (DSC) can be achieved on molecular photodissociation in the dipole limit, using single-cycle (FWHM) laser pulses in the terahertz (THz) regime. As the laser-molecule interaction follows the instantaneous electric field through the permanent dipoles, the molecular potentials dynamically oscillate and so does the crossings between them. In this paper, we consider rotating-vibrating diatomic molecules (2D description) and reveal the interplay between the dissociating wave packet and the dynamically fluctuating crossing seam located in the configuration space of the molecules spanned by the R vibrational and $\theta$ rotational coordinates. Our showcase example is the widely studied lithium-fluoride (LiF) molecule for which the two lowest $\Sigma$ states are nonadiabatically coupled at an avoided crossing (AC), furthermore a low-lying pure repulsive $\Pi$ state is energetically close. Optical pumping of the system in the ground state thus results in two dissociation channels: one indirect route via the AC in the ground $\Sigma$ state and one direct path in the $\Pi$ state. We show that applying THz control pulses with specific time delays relative to the pumping, can significantly alter the population dynamics, as well as, the kinetic energy and angular distribution of the photofragments.

Highlights

Thanks to the continuously developing laser technology, which has made it possible to generate light pulses with the length of a few femtoseconds or a few hundred attoseconds, quantum control techniques are among the most powerful tools of physics both in fundamental research and in practical applications
In the present work we focus on a different subject and control the dynamics by a single-cycle terahertz (THz) laser pulse, the molecular rotation is included in the numerical simulations so as to describe accurately the photodissociation process
The initial nuclear wave packet [] of this isotropic distribution was built from the rotational J = 0 and the vibrational ν = 0 ground state of the 1 electronic state

Summary

Introduction

Thanks to the continuously developing laser technology, which has made it possible to generate light pulses with the length of a few femtoseconds or a few hundred attoseconds, quantum control techniques are among the most powerful tools of physics both in fundamental research and in practical applications. Efforts were invested to apply the dynamic Stark effect (DSE) for control of chemical dynamical processes [28,29,30,31,32,33,34,35]. It can be resonant or nonresonant depending on the applied light frequency. Light-induced or “dressed” adiabatic potentials are formed, which incorporate the laser-molecule coupling effects. Numerous theoretical and experimental studies have demonstrated that the light-induced nonadiabatic phenomena

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