Observing Vibrational Quantum Beating in the Ultrafast Predissociation of SF 6

Quantum coherence plays a fundamental role in driving ultrafast molecular dynamics, but its observation in highly excited states of polyatomic molecules remains rare. Here, using time-resolved photoelectron spectroscopy (TRPES), we report the observation of coherent vibrational quantum beating in the predissociation dynamics of the SF 6 molecule, triggered by a 14.1-eV extreme ultraviolet laser pulse. We observe the temporal oscillation profile of TRPES intensity with a period of 318 fs, arising from the interference between different vibrational states separated by 0.013 eV. Supported by ab-initio calculations of potential-energy surfaces, we identify the vibrational states responsible for these observations and extract the lifetimes of both coherences and populations. This work opens pathways to understand and ultimately control the role of coherence in photochemical processes of complex molecular systems.