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Optical Engineering

Visible emission from C2 and CN during cw laser-irradiated graphite
Author(s): William Bauer; Charlie Fox; Ryan Gosse; Glen Perram
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Paper Abstract

Porous graphite samples were irradiated with up to 3.5  kW/cm2 and 1 MJ deposited energy from a continuous wave ytterbium 1.07-μm fiber laser. Visible emission spectroscopy reveals C2 Swan (d3Πg−a3Πu) Δv=±2,±1, and 0 sequences, CN red (A2Π−X2Σ+) Δv=−4,−3 sequences, CN violet (B2Σ+X2Σ+) Δv=+1,0 sequences, and Li, Na, and K2P3/2,1/22S1/2 doublets. Surface temperatures increased from ∼2500  K at 0.7  kW/cm2 to ∼4000  K at 3.5  kW/cm2. Spectral emissivity at 3.9  μm ranging from 0.74 to 0.93 increases by ∼8% after laser irradiation. Spectral simulations demonstrate that the ratio of C2(d) and CN(A) column densities are independent of sample porosity. Column densities increase from 0.00093 to 1.6×1012  molecules/cm2 for CN(A) and 0.00014 to 1.4×109  molecules/cm2 for C2(d) as laser intensity increases from 1.4 to 3.5  kW/cm2. Surface temperatures increase by 134 K and CN(A) and C2(d) emissions increase by 100% and 4200%, respectively, in stagnation air flow of 5  m/s.

Paper Details

Date Published: 20 September 2016
PDF: 10 pages
Opt. Eng. 56(1) 011017 doi: 10.1117/1.OE.56.1.011017
Published in: Optical Engineering Volume 56, Issue 1
Show Author Affiliations
William Bauer, Air Force Institute of Technology (United States)
Charlie Fox, Air Force Institute of Technology (United States)
Oak Ridge Institute for Science and Education (United States)
Ryan Gosse, Air Force Research Lab. (United States)
Glen Perram, Air Force Institute of Technology (United States)

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