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 ¹B_2u (ππ*) and ¹B_3u (nπ*) states, while recent theoretical and experimental studies have revealed that the ¹A_u (nπ*) state also participates in the dynamics, inspiring strong interest in electronic and vibrational coherence involving both the ¹B_3u and ¹A_u 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 ¹B_3u and ¹A_u states may also occur in solution.