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Title: Expansion Dynamics of Ultrafast Laser Produced Plasmas in the Presence of Ambient Argon

In this paper, we report the emission features of fs laser ablated brass plasma plumes at various Ar background pressure levels ranging from vacuum to atmospheric conditions. Spectrally integrated 2D-imaging of plasma self-emission showed several interesting features at various pressure levels which consists of plume morphological changes, increase in persistence, confinement, and internal structures. Spatially resolved wavelength dispersed images of the plume were recorded for characterizing the spectral features at various pressure levels and also used for obtaining spatial distribution of Cu I and Zn I species in the plume, signal to noise ratios and fundamental parameters of the plasma; viz. temperature and density. The spatial evolution of excitation temperature and density showed significant changes at various ambient pressure levels and these results were correlated to morphological changes seen in the plume images. Optimum signal to background ratios for emission lines were observed in the moderate pressure range (~ 1-10 Torr). Optical time-of-flight profiles were used to study time evolution of various species in the plume and noticed oscillations at intermediate pressure levels. Possible mechanisms for observed changes in plume shape, optical emission intensity, and dual peak structures in time-of-flight profiles were discussed.
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Journal Article
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Journal Name: Journal of Applied Physics, 116(13):133301
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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Country of Publication:
United States
ultrafast laser ablation; laser produced plasma; LIBS; plasma hydrodynamics; emission