Electronic dynamics in liquids are of fundamental importance, but time-resolved experiments have so far remained limited to the femtosecond time scale. We report the extension of attosecond spectroscopy to the liquid phase. We measured time delays of 50 to 70 attoseconds between the photoemission from liquid water and that from gaseous water at photon energies of 21.7 to 31.0 electron volts. These photoemission delays can be decomposed into a photoionization delay sensitive to the local environment and a delay originating from electron transport. In our experiments, the latter contribution is shown to be negligible. By referencing liquid water to gaseous water, we isolated the effect of solvation on the attosecond photoionization dynamics of water molecules. Our methods define an approach to separating bound and unbound electron dynamics from the structural response of the solvent.

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In a recent comment, 1 Ruth Signorell raises a number of issues that she considers to question the validity of our approach to determine mean free paths for electron scattering in liquid water 2 and our comparison with the results on amorphous ice by Michaud, Wen, and Sanche. 3 Here, we show that these critiques are unjustified, being either unfounded or based on misconceptions by the author of the comment. We nevertheless welcome the opportunity to further clarify certain aspects of our work that we did not discuss in detail in our letter. 2 Our reply is structured as the comment, i.e., the four main points of the comment are discussed individually.(1) Signorell incorrectly claims that the effective attenuation length (EAL) as defined in our work is different from the definition used in the analysis of the measurements of Suzuki et al. 4 , which we take as input for our simulations.Both our work and the analysis of Suzuki et. al. are based on the same standard definition of the EAL, i.e., the electron signal S(z) detected outside the liquid decays exponentially with the distance from the point of ionization to the surface z,and the EAL r EAL is the width parameter of 0 r EAL ionization depth 0 N photoelectron signal Ne z/rEAL Figure 1: Exponential decay of the photoelectron signal with ionization depth. The area under the exponential function is equal to the area in the box given by N × r EAL , which is used by Suzuki et al. 4 to determine r EAL experimentally. 1 arXiv:2003.05820v1 [physics.chem-ph]

Shape resonances play a central role in many areas of science, but the real-time measurement of the associated many-body dynamics remains challenging. Here, we present measurements of recoil frame angle-resolved photoionization delays in the vicinity of shape resonances of CF 4 . This technique provides insights into the spatiotemporal photoionization dynamics of molecular shape resonances. We find delays of up to ∼600 as in the ionization out of the highest occupied molecular orbital (HOMO) with a strong dependence on the emission direction and a pronounced asymmetry along the dissociation axis. Comparison with quantum-scattering calculations traces the asymmetries to the interference of a small subset of partial waves at low kinetic energies and, additionally, to the interference of two overlapping shape resonances in the HOMO-1 channel. Our experimental and theoretical results establish a broadly applicable approach to space-and time-resolved photoionization dynamics in the molecular frame.

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