A Quantum Control Spectroscopy Approach by Direct UV Femtosecond Pulse Shaping

A quantum control spectroscopy (QCS) approach using directly shaped UV excitation pulse is demonstrated. Ultrafast tailored pulses in the region of 310-335 nm are combined with transient absorption to investigate reactive pathways in the excited state of (2,2´-bipyridyl)-3,3´-diol BP(OH)₂. In particular, we apply QCS in the disentanglement of the competing excited-state intramolecular proton-transfer (ESIPT) channels of BP(OH)₂. Our results challenge parallel reactive pathways in the excited state and suggest a newer model based on an extremely fast sequential double ESIPT process.