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Published on: June 9, 2016
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Investigating plasma morphology at material boundaries under varying ambient pressures
Megha Mohan1, David Prochazka2, Yi You3
1Central European Institute of Technology, Brno University of Technology, Purkyňova 656/123, CZ-61200, Brno, Czech Republic.
Talanta
|May 30, 2025
Summary
Laser-Induced Breakdown Spectroscopy (LIBS) plasma homogeneity is affected by material boundaries. Varying ambient pressure influences plasma asymmetry and elemental distribution, impacting quantitative analysis accuracy.
Area of Science:
- Analytical Chemistry
- Materials Science
- Spectroscopy
Background:
- Laser-Induced Breakdown Spectroscopy (LIBS) is a common elemental analysis method that often assumes plasma homogeneity.
- Microscale LIBS analysis can be affected by sample heterogeneities, particularly at material boundaries, leading to plasma plume inhomogeneity.
- This inhomogeneity can significantly compromise the accuracy of quantitative elemental analysis.
Purpose of the Study:
- To investigate the influence of ambient pressure on plasma morphology and spectral characteristics during Laser-Induced Breakdown Spectroscopy (LIBS) ablation at a Cu-Sn material boundary.
- To compare these findings with LIBS analysis of homogeneous alloys under identical pressure conditions.
- To understand how pressure-dependent plasma expansion affects elemental distribution and accuracy in heterogeneous material analysis.
Main Methods:
- Utilized varying ambient pressures (7-1000 mbar) for Laser-Induced Breakdown Spectroscopy (LIBS) ablation at a well-defined Cu-Sn boundary and homogeneous alloys.
- Employed plasma imaging with bandpass filters and spectroscopy to analyze elemental distribution, signal-to-noise (SNR), and signal-to-background (SBR) ratios.
- Applied Radon transform-based 3D reconstruction to visualize and quantify plasma morphology and asymmetry.
Main Results:
- 3D reconstructions showed significant plasma asymmetry when ablating at the Cu-Sn boundary, unlike the near-axial symmetry for homogeneous alloys.
- Lower ambient pressures resulted in persistent elemental separation in the plasma plume.
- Higher pressures led to increased collisional mixing and plasma homogenization, with consistently lower SNR and SBR for boundary ablation compared to homogeneous samples.
Conclusions:
- Ablation at material boundaries creates plasma inhomogeneities in LIBS, impacting quantitative analysis.
- Ambient pressure plays a critical role in mitigating or exacerbating these inhomogeneities through collisional mixing.
- Accurate elemental mapping of fine heterogeneous structures using LIBS requires careful consideration of boundary effects and pressure conditions.
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