ECAMP 15

Attosecond science addresses the dynamics of electrons on their natural time scale, and much progress has been made in the understanding of processes such as attosecond charge migration; attosecond photoionization times; and the driven attosecond dynamics that takes place during high-harmonic generation (HHG). The majority of attosecond studies have been performed on atoms and molecules in the gas phase, with recent extensions of HHG into crystalline solids. However, many organic molecules of interest exist most naturally in the liquid phase, and only a few studies have emerged on the influence of a liquid environment on the initiation, evolution, and probing of attosecond dynamics.

In this talk I will report on two recent efforts studying attosecond dynamics in solutions, in which a low concentration of a molecule of interest is mixed into a liquid solvent: (i) We have compared core-hole-initiated charge migration in fluoroaniline in different solutions, using time-dependent density functional theory calculations. We find that the charge migration period, which is less than 1 fs, stays relatively constant independent of the solvent. However, in the solutions we find finite dephasing times for the dynamics that depend strongly on the solvent, suggesting that solute-solvent interactions indeed have an influence on the attosecond electron dynamics. (ii) In a joint experiment-theory work, we have studied HHG in different solutions of halobenzenes (PhX) and methanol (MeOH). Our experimental results show evidence of local order in the solvation of fluorobenzene (PhF) in MeOH. This manifests as a near-complete suppression of a single harmonic in the solution, which is absent in each of the pure liquids and absent in other PhX-MeOH solutions. We interpret the results in terms of a solvation shell that is formed in the PhF-MeOH solution and acts like a local barrier in the HHG process.