Polarization-Resolved Transient Absorption of the Strong-Field Ionization of Liquid Water*

Spectroscopically resolving the ultrafast valence electronic and nuclear changes involved in the photoionization of liquid water is a long-standing experimental goal. The orbital selectivity of strong-field ionization is a powerful tool for elucidating molecular pathways in the gas phase; we seek to leverage this to study the early states of liquid water upon being photoionized, offering a complementary set of experiments to two-photon and deep-UV excitation.

Here we present new results from the strong-field transient absorption of liquid water, looking at dynamics following valence to continuum transitions. In particular, we use the relative polarization between the strong-field pump and the broadband probe to study the strong-field excitation of liquid water in the tunneling regime, with sub-10 fs time resolution. These measurements aim to explore the importance of electronic delocalization in the strong-field ionization of extended systems.