Coherent Control of Bond Making

TL;DR

This paper demonstrates the first coherent control of bond making in photo-induced reactions, showing that pulse shaping can enhance or suppress molecule formation through vibrational dynamics and Raman transitions.

Contribution

It introduces a novel experimental and theoretical approach to control bimolecular reactions using femtosecond pulse shaping and phase optimization.

Findings

Enhanced magnesium dimer yield with positively chirped pulses

Suppressed yield with negatively chirped pulses

Improved control via closed-loop phase optimization

Abstract

We demonstrate for the first time coherent control of bond making, a milestone on the way to coherent control of photo-induced bimolecular chemical reactions. In strong-field multiphoton femtosecond photoassociation experiments, we find the yield of detected magnesium dimer molecules to be enhanced for positively chirped pulses and suppressed for negatively chirped pulses. Our ab initio model shows that control is achieved by purification via Franck-Condon filtering combined with chirp-dependent Raman transitions. Experimental closed-loop phase optimization using a learning algorithm yields an improved pulse that utilizes vibrational coherent dynamics in addition to chirp-dependent Raman transitions. Our results show that coherent control of binary photo-reactions is feasible even under thermal conditions.