Picosecond imaging of dynamics of solvated electrons during femtosecond laser-induced plasma generation in water

TL;DR

This study visualized the ultrafast dynamics of solvated electrons during femtosecond laser-induced plasma formation in water, revealing rapid changes in optical properties linked to plasma generation.

Contribution

It introduces a sub-picosecond pump-probe absorption imaging technique to observe solvated electron dynamics during femtosecond laser plasma generation in water.

Findings

Rapid increase in optical density at 800 nm 7-9 ps after excitation.

No two-step OD increase observed at 400 nm, indicating fast absorption coefficient changes.

Structural and electronic modulation of solvated electrons linked to plasma formation.

Abstract

The dynamics of solvated electrons were visualized using absorption imaging with sub-picosecond time resolution based on a pump-probe measurement during the early stages of femtosecond laser-induced plasma generation in water. The solvated electrons were generated by the propagation of a femtosecond laser pump pulse. In the area with a pump laser intensity over 2x10^13 W/cm2, where a high density of free electrons was produced, solvated electrons exhibited an additional rapid increase in optical density (OD) at 800 nm, 7-9 ps after the pump pulse excitation. In contrast, no two-step increase in OD was observed when probed at 400 nm, suggesting that the absorption coefficient of the solvated electrons rapidly changed around 800 nm after femtosecond laser excitation for a few picoseconds. This observation might indicate the structural and electronic modulation of solvated electrons owing to the high density of free electrons in water, accompanied by femtosecond-laser-induced plasma generation.