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 for particular pairs of states, the electronic phase remains well defined despite vibrational motion along many degrees of freedom. We explore the time dependence of the electronic coherence and show how it is modulated by the time-dependent vibrational overlap between the two wave functions. Our measurements are interpreted with electronic structure calculations and compared to analytic expressions for the electronic coherence.