Effects of the absorption coefficient on resonant infrared laser ablation of poly(ethylene glycol)

We describe experiments on resonant infrared laser ablation of poly(ethylene glycol) (PEG) at two different resonant excitation wavelengths and for different molecular weights of PEG. The two resonant wavelengths correspond to different stretching vibrations of the polymer and have absorption coeffi...

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Bibliographic Details
Published in:Journal of applied physics 2009-01, Vol.105 (2)
Main Authors: Johnson, S. L., Schriver, K. E., Haglund, R. F., Bubb, D. M.
Format: Article
Language:English
Subjects:
ABLATION
ABSORPTION
BOILING
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
EXCITATION
EXPLOSIONS
INFRARED SPECTRA
LASERS
MOLECULAR WEIGHT
PLUMES
POLYETHYLENE GLYCOLS
TIME RESOLUTION
WAVELENGTHS
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Summary:We describe experiments on resonant infrared laser ablation of poly(ethylene glycol) (PEG) at two different resonant excitation wavelengths and for different molecular weights of PEG. The two resonant wavelengths correspond to different stretching vibrations of the polymer and have absorption coefficients that differ by roughly an order of magnitude. Ablation via excitation of the O–H terminal group stretching mode at 2.94 μm, the weaker of the two absorptions, is delayed in time by several microseconds with respect to ablation at 3.47 μm, the more strongly absorbing C–H stretching mode of the polymer. Time-resolved plume shadowgraphs along with ablation rate measurements for the two modes reveal that the absorption coefficient strongly affects the physical characteristics of the ejecta and plume, as well as the time scale for material removal. Temperature-rise calculations demonstrate that phase explosion is likely the operative mechanism in ablation at the C–H mode, while normal boiling may play a role in material removal at the O–H mode.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3043883