低真空下紫外激光烧蚀铜诱导发光的机理

采用时间与空间分辨的光谱测量技术,测量了在低真空下XeCl紫外激光烧蚀金属Cu诱导产生等离子体发光羽的发射光谱随时间和空间的强度分布,利用快速同步照相的方法获得了发光羽的相片,结果发现发光羽的不同区域有不同的颜色特征。根据实验结果建立了非常可能的激光烧蚀诱导发光的理论模型,认为不同区域的主要发光机理不同,连续辐射背景光来自近靶处高能电子的运动而产生的轫致辐射;原子线的产生来自电子碰撞传能以及电子与离子的复合激发;离子线的产生来自电子与离子碰撞传能激发。此模型不仅能解释单一激发模型所能解释的实验现象,而且还能够很好地解释单一模型所不能解释的实验现象,低真空下紫外激光烧蚀铜诱导发光的机理与常压下相似,在此实验条件下可以更准确地揭示诱导发光的机理。

The Emission Studies on Ultraviolet Laser Ablation of Copper in Low Pressure

Owing to the highly transitory behaviour of laser-produced plasma, it is difficult to found the mechanism of plasma radiating because of the process of ablation being complicated.It is the most important to characterize the laser produced plasma (LPP)in a time- and space-resolved way. In the paper,optical emission spectroscopy is used to characterize the plasma produced by 308 nm,20 ns XeCl excimer laser ablation of Cu target in low pressure. Time- and spatial-resolved measurements of optical emission produced by XeCl excimer laser ablation of Cu in low pressure were reported. The pressure of ablation chamber was 1 Pa air. The temporal variation of the spectrum lines intensities was analyzed.The plasma plume photograph from XeCl excimer laser ablation of Cu was taken by camera in air with pressure of 1 Pa. The experimental results show that the plume has different colour in different region,the core region of the plume is white, the middle region of the plume is yellow and purple etc, the outskirts region of the plume is green.The experimental results may be explained using a theory model based on that plume is made of three region and the region detail species excitation mechanism is different from each another. The continuum background emission comes from the Bremsstrublung emission of electrons ejected from target. The excited copper atoms and ions may be produced from different mechanism, the atoms excitation mechanism in plume is electron collision energy transfer and recombination of electron and ion, but the ions excitation mechanism in plume is electron collision energy transfer only. The results show that the most possible plume radiation mechanism is dual excitation model,it can be used to explain the experimental results that the simple excitation model can to do, and can be used to explain the experimental results that the simple excitation model can not to do. We found that the plume radiation mechanism obtained in low pressure is accuracy and direct to that of at the pressure of one atmosphere.