Optimal control of multi-photon dissociation and ionization processes in small NamKn clusters

Abstract

Closed loop optimization of fs pulse shapes is investigated on the model systems consisting of small mixed alkali clusters. By controlling the photo-excited wave packet dynamics the multi-photon fragmentation and ionization of the Na_mK_n clusters are optimized. The resultant optimized pulse shapes carry fingerprints of the chosen dynamical pathways of the involved molecules. The dependence of fragmentation with cluster size is additionally investigated by gradually shifting the cluster size distribution towards larger masses. The resulting modification of the optimized pulse forms offers new insights into competing fragmentation channels during the control process. Characteristic motions of the involved wave packets are proposed to explain the optimized dynamic pathways. In particular, the steering of the wave packet in the trimer Na₂K by the optimized pulse can be described in terms of avoiding the predissociative curve crossing and thereby achieving an effective and selective fragmentation.