The emission characteristics of a laser-ablated calcium fluoride CaF₂ plasma have been investigated using time and space optical emission spectroscopy. The plasma-plume was produced by focusing 266 nm, 15 ns pulses from a Nd: YAG laser on a calcium fluoride crystal substrate placed in a vacuum chamber. The emission observed in the plasma region is due to electronic relaxation of excited neutral Ca and F, ionic fragments Ca²⁺, Ca⁺ and F⁺ and molecular features of CaF (A²Π- X²Σ⁺, B²Σ⁺- X²Σ⁺ and C²Π- X²Σ⁺) band systems. Plasma species were analyzed both as a function of the delay from the laser pulse incidence and location from the target surface. Spectroscopic diagnostics were employed to estimate time-resolved electron densities, electron temperatures and velocity expansion of different species. The results show a faster decay of the continuum emission, ionic F⁺, Ca²⁺, Ca⁺, F species than in the case of neutral Ca atoms and molecular species of CaF. Different excitation temperatures were measured by comparing Ca and F atomic/ionic Saha-local thermodynamic equilibrium (LTE) spectra with experimental ones at various delay times after the ablation event. Vibrational temperatures of CaF were assessed from the temporal analysis of the A²Π - X²Σ⁺ Δv = 0 band sequence molecular emission. We observed a non-equilibrium plasma although the plasma is found to maintain partial LTE.

已经使用时间和空间光学发射光谱研究了激光烧蚀氟化钙 CaF ₂等离子体的发射特性。等离子体羽是通过将来自 Nd:YAG 激光器的 266 nm、15 ns 脉冲聚焦在置于真空室中的氟化钙晶体基板上而产生的。在等离子体区域观察到的发射是由于激发的中性 Ca 和 F、离子碎片 Ca ²⁺、Ca ⁺和 F ^{+ 的}电子弛豫以及 CaF (A ² Π- X ² Σ ⁺、B ² Σ ⁺ - X ² Σ ⁺和 C ² Π- X ² Σ⁺ ) 波段系统。等离子体种类作为激光脉冲入射延迟和目标表面位置的函数进行分析。光谱诊断被用来估计不同物种的时间分辨电子密度、电子温度和速度膨胀。结果显示连续谱发射、离子 F ⁺、Ca ²⁺、Ca ⁺、F 物质比中性 Ca 原子和 CaF 分子物质的衰减更快。通过在烧蚀事件后的不同延迟时间将 Ca 和 F 原子/离子 Saha 局部热力学平衡 (LTE) 光谱与实验光谱进行比较来测量不同的激发温度。CaF 的振动温度是根据 A 的时间分析评估的² Π - X ² Σ ⁺ Δv = 0 带序分子发射。尽管发现等离子体维持部分 LTE，但我们观察到了非平衡等离子体。