Ultrafast decay dynamics of water molecules excited to electronic D[combining tilde]' and D[combining tilde]'' states: a time-resolved photoelectron spectroscopy study.

ABSTRACT

The ultrafast decay dynamics of water molecules excited to D[combining tilde]'1B1 and D[combining tilde]''1A2 states is studied by combining two-photon excitation and time-resolved photoelectron imaging methods. The lifetime of the D[combining tilde]'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 D[combining tilde]''1A2(000) state decays with a lifetime of 4.1 ± 0.2 ps, while in the D2O D[combining tilde]''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 D[combining tilde]'' → C[combining tilde] pathway, induced by Coriolis interaction.