Thomas Weinacht

I will discuss time resolved experiments that can probe non-adiabatic excited state dynamics. A single broadband (~5 fs) laser pulse can be shaped [1] to generate a pump-probe pulse pair, with the “pump” pulse launching an excited state wave packet and the “probe” pulse ionizing the molecule, in a multiphoton driven version of time-resolved photoelectron spectroscopy (TRPES). The advantage of this approach is that one can use the high time resolution and control over pulse shape available from near IR and optical pulses. This allows for following non-adiabatic dynamics and probing phase coherence [2], by varying the amplitude, delay and phase between pulses independently with very fine control. The experiments make use of velocity map imaging to determine the full momentum distribution of the electrons produced by the resonance enhanced multiphoton ionization.  These measurements are interpreted with the help of electronic structure calculations.

[1] Anthony Catanese, Brian Kaufman, Chuan Cheng, Eric Jones, Martin Cohen, Thomas Weinacht, Acousto-optic modulator pulse-shaper compression of octave-spanning pulses from a stretched hollow-core fiber, OSA Continuum (2021), 3176-3183 [2] Brian Kaufman, Tamas Rozgonyi, Philipp Marquetand, Thomas Weinacht, Coherent control of internal conversion in strong-field molecular ionization, Physical Review Letters (2020): 053202.