Terahertz Polaron Oscillations of Electrons Solvated in Liquid Water

TL;DR

This study investigates the nonlinear terahertz response of solvated electrons in liquid water, revealing persistent oscillations linked to coherent polaron dynamics involving coupled electron-water motions.

Contribution

It provides new insights into the terahertz-induced oscillations of solvated electrons and identifies their origin as coherent polaron oscillations in liquid water.

Findings

Oscillations persist up to 30 ps after excitation.

Oscillation frequency increases with electron concentration from 0.2 to 1.5 THz.

Oscillatory response attributed to impulsively excited coherent polarons.

Abstract

The terahertz (THz) response of solvated electrons in liquid water is studied in nonlinear ultrafast pump-probe experiments. Free electrons with concentrations from c_e = 4 to 140 \times 10-6 moles/liter are generated by high-field THz or near-infrared multiphoton excitation. The time-resolved change of the dielectric function as mapped by broadband THz pulses exhibits pronounced oscillations persisting up to 30 ps. Their frequency increases with electron concentration from 0.2 to 1.5 THz. The oscillatory response is assigned to impulsively excited coherent polarons involving coupled electron and water shell motions with a frequency set by the local electric field.