Oguri Katsuya, Okano Yasuaki, Nishikawa Tadashi, Nakano Hidetoshi
NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan.
Phys Rev Lett. 2007 Oct 19;99(16):165003. doi: 10.1103/PhysRevLett.99.165003. Epub 2007 Oct 18.
We study the temperature evolution of aluminum nanoparticles generated by femtosecond laser ablation with spatiotemporally resolved x-ray-absorption fine-structure spectroscopy. We successfully identify the nanoparticles based on the L-edge absorption fine structure of the ablation plume in combination with the dependence of the edge structure on the irradiation intensity and the expansion velocity of the plume. In particular, we show that the lattice temperature of the nanoparticles is estimated from the L-edge slope, and that its spatial dependence reflects the cooling of the nanoparticles during plume expansion. The results reveal that the emitted nanoparticles travel in a vacuum as a condensed liquid phase with a lattice temperature of about 2500 to 4200 K in the early stage of plume expansion.
我们利用时空分辨X射线吸收精细结构光谱研究了飞秒激光烧蚀产生的铝纳米颗粒的温度演化。我们结合烧蚀羽流的L边吸收精细结构以及边结构对辐照强度和羽流膨胀速度的依赖性，成功识别了纳米颗粒。特别是，我们表明纳米颗粒的晶格温度可从L边斜率估算得出，其空间依赖性反映了羽流膨胀过程中纳米颗粒的冷却情况。结果表明，在羽流膨胀的早期阶段，发射出的纳米颗粒在真空中以凝聚液相的形式传播，晶格温度约为2500至4200K。
