Closed-loop learning control of isomerization using shaped ultrafast laser pulses in the deep ultraviolet.

We demonstrate the use of shaped ultrafast laser pulses in the deep ultraviolet to control the ring opening isomerization of 1,3-cyclohexadiene to form 1,3,5-hexatriene. The experiments are performed with a gas phase sample and the isomerization yield is probed with dissociative ionization driven by a time-delayed, intense infrared laser pulse. Differences in the electronic structure of the ions for the two isomers, as shown by ab initio calculations, result in very different fragmentation products following strong-field ionization. We find that a shaped pulse yields a approximately 37% increase in the isomerization over an unshaped laser pulse.