Long Lived Electronic Coherences in Molecular Wave Packets Probed with Pulse Shape Spectroscopy

We explore long lived electronic coherences in molecules using shaped ultrafast laser pulses to launch and probe entangled nuclear-electronic wave packets. We find that under certain conditions, the electronic phase remains well defined despite vibrational motion along many degrees of freedom. The experiments are interpreted with the help of electronic structure calculations which corroborate our interpretation of the measurement

Direct Observation of Entangled Electronic-Nuclear Wave Packets

We present momentum resolved covariance measurements of entangled electronic-nuclear wave packets created and probed with octave spanning phaselocked ultrafast pulses. We launch vibrational wave packets on multiple electronic states via multi-photon absorption, and probe these wave packets via strong field double ionization using a second phaselocked pulse. Momentum resolved covariance mapping of the fragment ions highlights the nuclear motion, while measurements of the yield as a function of the relative phase between pump and probe pulses highlight the electronic coherence. The combined measurements allow us to directly visualize the entanglement between the electronic and nuclear degrees of freedom and follow the evolution of the complete wavefunction

High Repetition-Rate Pulse Shaping of a Spectrally Broadened Yb Femtosecond Laser

We demonstrate compression and shaping of few cycle pulses from a high average power Ytterbium laser system. The pulses from a commercial 20 W, 100 kHz Yb laser system are spectrally broadened in two-stages using gas-filled, stretched hollow-core fibers and then compressed and shaped in an acousto-optic modulator-based pulse-shaper. The pulse-shaper allows for compression, characterization, and shaping all in one system, producing ~10 fs pulses with 50 uJ of energ

Model for describing resonance-enhanced strong-field ionization with shaped ultrafast laser pulses

We present a simple model for calculating strong field atomic and molecular ionization dominated by Freeman resonances. Our model combines multiphoton coupling between bound states, including dynamic Stark shifts, with coupling to a discretized continuum. The simplicity of the model allows us to interpret pulse shape dependent strong field ionization yields and to demonstrate the relevance of strong field atomic/molecular phase matching to ionization as well as bound state population transfer. Comparison with experimental measurements demonstrates that the calculations capture the essence of the pulse shape dependent ionization yields