Optical properties of water relaxing after intense laser exposure

The dynamics of the optical properties of water bulk exposed to femtosecond radiation (Ti-sapphire laser, wavelength 800 nm, intensity ∼1013W/cm2) was studied in the time window of ≈1.5ns using a pump–probe technique. Both the refractive index and absorbance were measured by femtosecond interferometric microscopy, which allowed us to gather deconvoluting quantitative data about the induced processes: solvation of excess electrons, geminate recombination, and development of cavitation. We found that the number of electrons produced by a strong, near infrared (NIR) field in the cavitation regime (<1019cm−3) is much lower than was previously thought. The obtained data clarify the mechanisms of laser energy deposition in water and are of crucial importance to understand intensive light action on aqueous-based systems.