The dynamics of the optical properties of water bulk exposed to femtosecond radiation (Ti-sapphire laser, wavelength 800 nm, intensity ${\sim}{10^{13}} {\rm W}/{{\rm cm}^2}$) was studied in the time window of $\approx 1.5\;{\rm ns}$ 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 (${ {\lt} 10^{19}}\;{{\rm cm}^{- 3}}$) 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.

中文翻译：

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强烈激光照射后水松弛的光学特性

飞秒辐射（钛蓝宝石激光器，波长800 nm，强度$ {\ sim} {10 ^ {13}} {\ rm W} / {{\ rm cm} ^ 2 } $}是使用泵浦探针技术在$ \约1.5 \; {\ rm ns} $的时间窗口中进行研究的。折光率和吸光度都是通过飞秒干涉显微镜测量的，这使我们能够收集有关诱发过程的反卷积定量数据：过量电子的溶剂化，双键重组以及空化的发展。我们发现在空化状态下由强近红外（NIR）场产生的电子数量（$ {{\ lt} 10 ^ {19}} \; {{\ rm cm} ^ {-3}} $）比以前认为的要低得多。所获得的数据阐明了激光能量在水中沉积的机理，对于理解水基体系上的强光作用至关重要。