Ultrafast decay dynamics of water molecules excited to electronic ′ and ′′ states: a time-resolved photoelectron spectroscopy study

Abstract

The ultrafast decay dynamics of water molecules excited to ′¹B₁ and ′′¹A₂ states is studied by combining two-photon excitation and time-resolved photoelectron imaging methods. The lifetime of the ′¹B₁(000) state of H₂O (D₂O) is determined to be 1.54 ± 0.1 (22.6 ± 1.6) ps, consistent with a previous high-resolution spectroscopic study. The H₂O ′′¹A₂(000) state decays with a lifetime of 4.1 ± 0.2 ps, while in the D₂O ′′¹A₂(000) state, two independent decay pathways are observed, with time constants of 0.55 ± 0.1 and 13 ± 1 ps, respectively. The former is proposed to be associated with a hitherto undocumented ′′ → pathway, induced by Coriolis interaction.