Closed-loop control of vibrational population in CO²⁺

An adaptive closed-loop feedback system is used to determine the optimal pulse shapes for manipulating the branching ratio of CO²⁺ following ionization by an intense laser pulse. For this target, selecting between the CO²⁺ and C⁺ + O⁺ final states requires control of the vibrational population distribution in the transient CO²⁺. The ability to both suppress and enhance CO²⁺ relative to C⁺ + O⁺ is observed, with shaped pulses surpassing a transform-limited pulse by factors of about 10 for suppression and 2 for enhancement. When optimizing small channels, such as non-dissociative CO²⁺, we demonstrate that a feedback signal obtained via a pulse counting technique is more robust than the more typical current mode signal collection. Furthermore, we demonstrate how the pulse counting technique allows control of a coincidence channel, specifically C⁺ + O⁺, by using logical electronic gates. Using these coincidence signals allows more specific final states to be incorporated into closed-loop control.