Decoherence and Relaxation of Vibrational Motion in Ultrafast Electronic Relaxation of Pyrazine in Solution.

We employed extreme-ultraviolet time-resolved photoelectron spectroscopy to investigate the decoherence and relaxation of vibrational motion of pyrazine in aqueous and ethanol solutions. Pyrazine has well-characterized vibronic interactions between the 1B2u (ππ*) and 1B3u (nπ*) states, while recent theoretical and experimental studies have revealed that the 1Au (nπ*) state also participates in the dynamics, inspiring strong interest in electronic and vibrational coherence involving both the 1B3u and 1Au states. Our results indicate that vibrational coherence in water and ethanol persists for approximately 300 fs, similar to that in the gas phase, suggesting that periodic electronic population transfer between the 1B3u and 1Au states may also occur in solution.