Rydberg state-mediated photoionisation of dissociating NaK wave packets in the B1Π state

The photoionisation dynamics of NaK molecules in the B1Π state is studied in both frequency and time domain by femtosecond laser spectroscopy. Comparison to model calculations shows that the photoionisation proceeds via intermediate-to-high-n Rydberg states. These Rydberg states act as Franck–Condon windows in the time-dependent experiment, and the molecular ions produced by autoionisation of the Rydberg states are shown to reflect the wave packet evolution in the B state. Consequently, Rydberg state-mediated photoionisation is proposed as a viable method for probing molecular wave packet dynamics.