A study is conducted on the detailed static and dynamic characteristics of plasma and the resulting emission spectral qualities generated by a femtosecond (fs) laser irradiation compared with those produced by nanosecond (ns) laser irradiation at a reduced ambient air pressure of 0.65 kPa. It is shown that both plasmas feature a tiny primary and a much larger secondary plasmas, which share the same hemispherical shape of roughly the same size at the appropriately chosen pulse energies. The resulted emission spectra in both cases exhibit one of the shock wave characteristics marked by a much stronger Zn triplet than its singlet emission lines. Further measurement of log(r)–log(t) of Cu I 521.8 nm emission line yields a slope of around 0.4, which is in good agreement with Sedov's equation derived for shock wave plasma. While exhibiting similar pressure-dependent emission intensities of Cu and Zn emission lines, the fs induced emission intensities are consistently lower than those induced by ns laser plasma. The estimated average temperature of the ns laser induced plasma (10 200 K) is only slightly higher than that induced by the fs laser (9800 K). The lower integrated emission intensity of fs plasma is related to previously reported lower electron density in fs laser-induced breakdown spectroscopy (fs-LIBS) and the faster decay of the associated continuum background, implying rapid diminution of ionized atoms and hence lower integrated emission intensity. Therefore, apart from cases demanding minimal surface damages, the simpler and less expensive ns-LIBS should be considered as a more favorable alternative for spectrochemical analysis. However, the applications to surface analysis do show that the fs laser offers higher detection sensitivity. A judicial selection is, therefore, strongly recommended.A study is conducted on the detailed static and dynamic characteristics of plasma and the resulting emission spectral qualities generated by a femtosecond (fs) laser irradiation compared with those produced by nanosecond (ns) laser irradiation at a reduced ambient air pressure of 0.65 kPa. It is shown that both plasmas feature a tiny primary and a much larger secondary plasmas, which share the same hemispherical shape of roughly the same size at the appropriately chosen pulse energies. The resulted emission spectra in both cases exhibit one of the shock wave characteristics marked by a much stronger Zn triplet than its singlet emission lines. Further measurement of log(r)–log(t) of Cu I 521.8 nm emission line yields a slope of around 0.4, which is in good agreement with Sedov's equation derived for shock wave plasma. While exhibiting similar pressure-dependent emission intensities of Cu and Zn emission lines, the fs induced emission intensities are consistently lower than those induced by ns laser plasma....

中文翻译：

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飞秒和纳秒激光诱导击穿光谱在还原环境空气中的激发机制和相应发射光谱的比较及其在表面分析中的性能

对等离子体的详细静态和动态特性以及飞秒 (fs) 激光辐照与纳秒 (ns) 激光辐照在 0.65 kPa 的降低环境气压下产生的发射光谱质量进行了研究。It is shown that both plasmas feature a tiny primary and a much larger secondary plasmas, which share the same hemispherical shape of roughly the same size at the appropriately chosen pulse energies. 在这两种情况下产生的发射光谱都表现出一种冲击波特性，其特征是锌三线态比其单线态发射线强得多。进一步测量 Cu I 521.8 nm 发射线的 log(r)–log(t) 产生大约 0.4 的斜率，这与推导出冲击波等离子体的 Sedov 方程非常吻合。虽然表现出类似的 Cu 和 Zn 发射线的压力相关发射强度，但 fs 诱导的发射强度始终低于 ns 激光等离子体诱导的发射强度。ns 激光诱导等离子体的估计平均温度 (10 200 K) 仅略高于 fs 激光诱导的等离子体 (9800 K)。fs 等离子体的较低积分发射强度与先前报道的 fs 激光诱导击穿光谱 (fs-LIBS) 中较低的电子密度和相关连续谱背景的更快衰减有关，这意味着电离原子的快速减少，因此积分发射强度较低. 因此，除了要求最小表面损伤的情况外，更简单且更便宜的 ns-LIBS 应被视为光谱化学分析的更有利替代方案。然而，表面分析的应用确实表明 fs 激光器提供更高的检测灵敏度。因此，强烈建议进行司法选择。 对等离子体的详细静态和动态特性以及飞秒 (fs) 激光辐照产生的发射光谱质量与纳秒 (ns) 激光辐照产生的发射光谱质量进行了研究。环境气压降低 0.65 kPa。It is shown that both plasmas feature a tiny primary and a much larger secondary plasmas, which share the same hemispherical shape of roughly the same size at the appropriately chosen pulse energies. 在这两种情况下产生的发射光谱都表现出一种冲击波特性，其特征是锌三线态比其单线态发射线强得多。进一步测量 Cu I 521 的 log(r)–log(t)。8 nm 发射线产生大约 0.4 的斜率，这与推导出冲击波等离子体的 Sedov 方程非常吻合。虽然表现出类似的 Cu 和 Zn 发射线的压力相关发射强度，fs 诱导的发射强度始终低于 ns 激光等离子体诱导的发射强度。...