The dissociation dynamics of acetophenone have been measured by ionizing with a tunable IR pulse (1150-1500 nm) to launch a wavepacket along the torsional coordinate of the phenyl-acetyl bond in the ground ionic “launch” state using tunnel ionization. The wavepacket can be subsequently probed using a low intensity 800 nm pulse to monitor the large-amplitude modulation in the benzoyl fragment (created through passage through a conical intersection) and parent yields as a function of pump-probe delay. The parent and benzoyl fragments are 180 degrees out of phase suggesting that the benzoyl fragment is created from direct photodissociation of the parent. Analysis of the potential surfaces reveals a conical intersection connecting the D2 state to a dissociative state. The wavepacket dynamics after tunnel ionization into the ground ionic state are in excellent agreement with molecular dynamics calculations. Increasing the intensity of the probe pulse initiates a wavepacket on higher-lying electronic surfaces that leads to dissociation of the parent into fragments including phenyl, acylium, and butadienyl radical cations. These three fragments are in phase with respect to pump probe time delay and can be used to extract a second component of the parent ion. The ability to monitor wavepacket dynamics on the femtosecond timescale suggests that tailoring the strong-field excitation pulse may allow for control of wavepacket evolution.<br/>

Creating multiple wavepackets during intense field, polyatomic dissociation using the radical cation launch state

256th National Meeting (2018)

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