Enhancing high-order above-threshold dissociation of H2+ beams with few-cycle laser pulses.

High-order (three-photon or more) above-threshold dissociation (ATD) of H + 2 has generally not been observed using 800 nm light. We demonstrate a strong enhancement of its probability using intense 7 fs laser pulses interacting with beams of H + 2 , HD + , and D + 2 ions. The mechanism invokes a dynamic control of the dissociation pathway. These measurements are supported by theory that additionally reveals, for the first time, an unexpectedly large contribution to ATD from highly excited electronic states.