We investigate the distribution of atoms and diatomic metal-oxide molecules in femtosecond laser-induced plasmas generated at and after the laser beam focal plane, where non-linear phenomena give rise to the formation of a weakly ionized air plasma channel. We use direct plasma imaging and optical emission spectroscopy to study plasma expansion, and the associated physical and chemical separation processes. Plasma splitting occurs upon the interaction of the weakly ionized plasma with the sample and is accompanied by a change in the spatio-temporal distribution of the molecules and atoms compared to sampling at the focus. Furthermore, molecular emission is favored at specific locations and is enhanced over atomic emission as the sample is moved underneath the laser focus. These findings support the ability to enhance or impede the formation of molecular versus atomic species at specific spatio-temporal locations in the laser-induced plasma.

中文翻译：

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飞秒激光诱导等离子体中金属原子及其双原子氧化物分子的时空分布

我们研究了在激光束焦平面处和之后产生的飞秒激光诱导的等离子体中原子和双原子金属氧化物分子的分布，其中非线性现象导致形成弱电离的空气等离子体通道。我们使用直接等离子体成像和光发射光谱法研究等离子体膨胀以及相关的物理和化学分离过程。等离子体分裂是在弱电离的等离子体与样品相互作用时发生的，并且与焦点采样相比，伴随着分子和原子的时空分布变化。此外，当样品移动到激光焦点下方时，分子发射在特定位置更受青睐，并且比原子发射得到增强。与激光诱导等离子体中特定时空位置的原子种类的关系。