Coherent Control of Ultrafast Bond Making and Subsequent Molecular Dynamics: Demonstration of Final-State Branching Ratio Control

TL;DR

This paper demonstrates the coherent control of ultrafast molecular bond formation and subsequent dynamics using shaped femtosecond laser pulses to manipulate the final state distribution of magnesium molecules.

Contribution

It introduces a method to control the branching ratio of molecular final states through chirped laser pulses in femtosecond photoassociation of thermal atoms.

Findings

Achieved control over Mg₂ molecule final states using chirped pulses.

Demonstrated high degree of quantum control in femtosecond photoassociation.

Established feasibility of coherent control from thermal initial states.

Abstract

Quantum coherent control of ultrafast bond making and the subsequent molecular dynamics is crucial for the realization of a new photochemistry, where a shaped laser field is actively driving the chemical system in a coherent way from the thermal initial state of the reactants to the final state of the desired products. We demonstrate here coherent control over the relative yields of Mg$_2$ molecules that are generated via photoassociation and subsequently photodriven into different groups of final states. The strong-field process involves non-resonant multiphoton femtosecond photoassociation of a pair of thermally hot magnesium atoms into a bound Mg$_{2}$ molecule and subsequent molecular dynamics on electronically excited states. The branching-ratio control is achieved with linearly chirped laser pulses, utilizing the different chirp dependence that various groups of final molecular states display for their post-pulse population. Our study establishes the feasibility of high degree coherent control over quantum molecular dynamics that is initiated by femtosecond photoassociation of thermal atoms.