Harilal S S, Kautz E J, Phillips M C
Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
James C. Wyant College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA.
Phys Rev E. 2021 Jan;103(1-1):013213. doi: 10.1103/PhysRevE.103.013213.
Time-resolved tunable laser absorption spectroscopy is used to characterize the physical properties of ultrafast laser-produced plasmas. The plasmas were produced from an Inconel target, with ≤0.4wt% Al, using ∼35fs, ∼800nm, ∼5mJ laser pulses at varying Ar background pressures from 1 to 100 Torr. The absorption spectrum of atomic Al is measured with high spectral and temporal resolution when the probe laser is stepped across the selected Al transition at 394.4 nm. Spectral fitting is used to infer linewidths, kinetic temperature, Al column density, and pressure broadening coefficient. The late time physical properties of plasmas are compared for various pressure levels. Our studies highlight that a significant lower state population exists even at early times of ultrafast laser-produced plasma evolution, and lower state population persistence decreases with increasing ambient pressure. We also show that the fundamental optical properties, such as pressure broadening, can be measured using ultrafast laser-produced plasmas combined with laser absorption spectroscopy.
时间分辨可调谐激光吸收光谱法用于表征超快激光产生的等离子体的物理性质。这些等离子体由含铝量≤0.4wt%的因科镍合金靶材产生，使用脉宽约35飞秒、波长约800纳米、能量约5毫焦的激光脉冲，氩气背景压力在1至100托之间变化。当探测激光在394.4纳米处选定的铝跃迁上扫描时，以高光谱和时间分辨率测量原子铝的吸收光谱。光谱拟合用于推断线宽、动力学温度、铝柱密度和压力展宽系数。比较了不同压力水平下等离子体的后期物理性质。我们的研究突出表明，即使在超快激光产生的等离子体演化的早期，也存在显著的低能级粒子数，并且低能级粒子数的持续时间随环境压力的增加而减少。我们还表明，诸如压力展宽等基本光学性质可以通过将超快激光产生的等离子体与激光吸收光谱法相结合来测量。
