Generation of radicals by laser-ablation and their application to beam source

通过激光消减，直接从固体靶中产生各种自由基。为了考察自由基源的适用性，用激光诱导荧光光谱研究了自由基团的性质。结果表明：(1)激光烧蚀YBa2Cu3O&lt；7-x&gt；(2)发现YO分子的动能高达10 eV，转动能分布在0.2 eV左右。结果表明，抛射分子的大部分能量是以动能的形式传输的。(4)Si_3N_4和BaTiO_3靶的速度分布符合二分量移位麦克斯韦分布。(5)Al原子束是通过对烧蚀产生的Al羽流进行切割而产生的，并通过成像激光诱导荧光光谱可视化了其密度分布的时间变化。实验结果表明，该方法可以很容易地产生高密度、高能的中性束。(6)研究了靶材的累积烧蚀对自由基射出的影响。结果发现，随着靶材的累积烧蚀，更多的微粒和更少的自由基被喷射出来。提出了一个描述目标退化过程的经验公式。

A variety of radicals was generated directly from solid targets by laser abation. Characteristics of the radicals were investigated by laser-induced fouorescence spectroscopy, in order to access the applicability for the radical sources. The results are summarized as follows.(1) Ba, Y,YO and BaO radicals were generated from a laser-ablated YBa_2Cu_3O_<7-x> target.(2) It was found that the kinetic energy of YO molecules reached upto 10eV.On the other hand, the rotational energy distribution was measured to be arount 0.2eV.It is shown that the most of the energy of the ejected molecules was transported as a kinetic energy.(3) Atomic species were mainly ejected from laser-ablated Al_2O_3, Si_3N_4 and BaTiO_3 targets(4) It was found that velocity distribution of ejected atoms were well described by a two-components shifted Maxwellian distribution.(5) Al atomic beam was generated by slitting the Al plume produced by the ablation and temporal developments of its density distribution were visualized by imaging laser-induced fluorescence spectroscopy. It was clearly demonstrated that high-density and high-energy neutral beam can be easily produced by the present technique.(6) The effect of the cumulative ablation of the targets on the ejection of radicals were investigated. It was found that more particulates and less radicals were ejected, as the target was ablated cumulative by. An empirical fomula which described the degradation of the target was proposed.