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

William Bauer; Charlie Fox; Ryan Gosse; Glen Perram

doi:10.1117/1.OE.56.1.011017

20 September 2016 ^{Visible emission from C₂ and CN during cw laser-irradiated graphite}

William Bauer, Charlie Fox, Ryan Gosse, Glen Perram

Author Affiliations +

Optical Engineering, Vol. 56, Issue 1, 011017 (September 2016). https://doi.org/10.1117/1.OE.56.1.011017

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 (d³Π_g−a³Π_u) 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 K²P_3/2,1/2−²S_1/2 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 C_₂(d) emissions increase by 100% and 4200%, respectively, in stagnation air flow of 5 m/s.

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William Bauer, Charlie Fox, Ryan Gosse, and Glen Perram "^{Visible emission from C₂ and CN during cw laser-irradiated graphite," Optical Engineering 56(1), 011017 (20 September 2016). https://doi.org/10.1117/1.OE.56.1.011017}

Published: 20 September 2016

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