Special Section on Laser Damage III

Visible emission from C2 and CN during cw laser-irradiated graphite

[+] Author Affiliations
William Bauer, Glen Perram

Air Force Institute of Technology, Department of Engineering Physics, 2950 Hobson Way, Wright Patterson Air Force Base, Ohio 45433, United States

Charlie Fox

Air Force Institute of Technology, Department of Engineering Physics, 2950 Hobson Way, Wright Patterson Air Force Base, Ohio 45433, United States

Oak Ridge Institute for Science and Education, 1299 Bethel Valley Road, Oak Ridge, Tennessee 37831-0117, United States

Ryan Gosse

Air Force Research Laboratory, Aerospace Systems Directorate, 2210 8th Street, B20146, Wright-Patterson Air Force Base, Ohio 45433, United States

Opt. Eng. 56(1), 011017 (Sep 20, 2016). doi:10.1117/1.OE.56.1.011017
History: Received June 9, 2016; Accepted August 22, 2016
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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 (d3Πga3Πu) Δv=±2,±1, and 0 sequences, CN red (A2ΠX2Σ+) Δv=4,3 sequences, CN violet (B2Σ+X2Σ+) Δv=+1,0 sequences, and Li, Na, and K2P3/2,1/2S1/22 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.

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© 2017 Society of Photo-Optical Instrumentation Engineers

Citation

William Bauer ; Charlie Fox ; Ryan Gosse and Glen Perram
"Visible emission from C2 and CN during cw laser-irradiated graphite", Opt. Eng. 56(1), 011017 (Sep 20, 2016). ; http://dx.doi.org/10.1117/1.OE.56.1.011017


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