Plasma−Particle Interactions in a Laser-Induced Plasma:  Implications for Laser-Induced Breakdown Spectroscopy

Abstract

The interaction between laser-induced plasmas and individual particles controls the rate of particle dissociation and subsequent atomic diffusion and emission processes, with implications for single-particle spectroscopy, as well as materials synthesis and other plasma sources. It is demonstrated through quantitative plasma imaging studies that discrete particles dissociate on a time scale of tens of microseconds within plasmas formed by 300-mJ Nd:YAG laser pulses. Significant spatial nonhomogeneity, as measured by localized atomic emission from particle-derived calcium atoms, persists on a comparable time scale, providing a measure of their average atomic diffusion rate of 0.04 m(2)/s. In addition, the resulting calcium atomic emission is explored using image analysis as well as traditional spectroscopic analysis.

Laser-Induced Breakdown Spectroscopy (LIBS), Part I: Review of Basic Diagnostics and Plasma—Particle Interactions: Still-Challenging Issues within the Analytical Plasma Community

“…To quantify such phenomena, researchers turned to spatially resolved spectral measurements and direct plasma imaging. Hohreiter and Hahn 260 were the first to directly image analyte species in a laser-induced plasma, as calcium atoms vaporized and dissociated from an individual glass microsphere and subsequently diffused into the surrounding plasma. Their study provided direct evidence of the actual timescales of particle vaporization and analyte diffusion, revealing that the plasma-particle interaction is initially limited to a localized spatial region about the analyte-containing particle.…”

Investigation of helium addition for laser-induced plasma spectroscopy of pure gas phase systems: Analyte interactions and signal enhancement

“…For example, the robustness of the gas-phase laser-induced breakdown process is often attributed to studies by Yalcin and co-workers, in which the overall plasma temperature and electron density were found to be remarkably independent of gas composition, including comparable plasma conditions for nitrogen, helium with 15% nitrogen, sulfur hexafluoride with 14% nitrogen, humidified nitrogen, and a nitrogen magnesium aerosol [32,33]. However, recent measurements of single aerosol particles in laser-induced plasmas reveal that plasma-particle interactions are confined to relatively small regions within the larger plasma volume [34], hence the potential to impact analyte signals independent of the overall plasma parameters is intriguing. With these comments in mind, the current study is focused on detailed analysis of the effect of helium addition on the analytical figures of merit and related plasma properties for analysis of purely gas-phase systems.…”

Application of Advanced Laser Diagnostics to High-Impact Technologies: Science and Applications of Ultrafast, Ultraintense Lasers

“…Recent results obtained by Hohreiter, 2006] suggests this is a real problem. They investigated the LIBS spectra of carbon in gas and solid phases.…”