激光能量对激光诱导Cu等离子体特征辐射强度、电子温度的影响

Effects of laser energy on electron temperature and the emission spectra intensities of copper plasma ablated with laser

利用Nd :YAG激光 (波长 10 6 4nm ,脉宽 10ns)烧蚀金属Cu靶获得等离子体。改变激光脉冲能量 ,观测到Cu的原子谱线和离子谱线随激光脉冲能量有不同的变化关系 ,但都在 330mJ/ pulse时 ,谱线强度达到最大 ,随后在 330mJ～ 370mJ/pulse间出现一小平台 ,能量继续增加 ,各谱线强度减小。同时 ,使用烧蚀Cu靶产生的五条原子谱线 (4 6 5 .11nm ,5 10 .5 5nm ,5 15 .32nm ,5 2 1.82nm ,5 2 9.2 5nm)的相对强度 ,在局部热力学平衡近似下 ,利用Boltzmann图的最小二乘法拟合 ,测定了不同激光能量下Cu等离子体的电子温度。随激光能量的增加 ,电子温度近似单调地从 1.0 2× 10 4K上升到 1.4 6× 10 4K后 ,反而有所下降。

Using Nd:YAG laser (with a wavelength of 1 064 nm and a pulse width of 10 ns) to ablate Cu target to get plasma spectra with different intensities of laser energy, we observe the different changes of CuⅠ and CuⅡ spectra as follows: the intensities of the atomic and ions lines of Cu plasma spectra have different changes with the increase of laser energy. The intensities of all lines get to maximum when laser energy is 330 mJ/pulse, then there is a small flat between 330 and 370 mJ/pulse of laser energy, and subsequently, the intensities of all lines gradually decrease with further increase of laser energy. Meanwhile, under the model of local thermodynamic equilibrium (LTE), we measure the electronic temperatures of Cu plasma at different intensities of laser energy according to the relative intensities of five lines. Our results show that the temperature ascends monotonously from 1.02×10 4 K to 1.46×10 4 K with the increase of laser energy, then it decreases along the further increment of laser energy.