Examining the role of the feedback signal in closed-loop control of molecular fragmentation*

Closed-loop control schemes incorporating feedback algorithms and shaped ultrafast laser pulses have been used to control a number of molecular processes. Using carbon monoxide as a model system, we have examined how the type of feedback signal delivered to the algorithm can influence the level of control and in some cases, help provide a better understanding of how the control is accomplished. Several feedback methods were examined, including using time-of-flight to select dissociation channels by kinetic energy release, isolating the C$^+$ + O$^+$ channel using a coincidence time-of-flight technique and using velocity map imaging to provide multi-dimensional momentum information in the feedback loop.