Strong Field Adiabatic Ionization Prepares a Launch State for Coherent Control.

We demonstrate that excitation of acetophenone with a strong field, near-infrared femtosecond pulse (1150-1500 nm) results in adiabatic ionization, producing acetophenone radical cation in the ground electronic state. The time-resolved transients of the parent and fragment ions probed with a weak 790 nm pulse reveal an order of magnitude enhancement of the peak-to-peak amplitude oscillations, ∼ 100 fs longer coherence time, and an order of magnitude increase in the ratio of parent to fragment ions in comparison with nonadiabatic ionization with a strong field 790 nm pulse. Equation of motion coupled cluster and classical wavepacket trajectory calculations support the mechanism wherein the probe pulse excites a wavepacket on the ground surface D0 to the excited D2 surface at a delay of 325 fs, resulting in dissociation to the benzoyl ion. Direct population transfer to the D2 state within the duration of a 1370 nm pump pulse eliminates wavepacket oscillation on the D0 state.