24 May 1993 Emissivity measurements of single levitated microparticles
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Proceedings Volume 1862, Laser Applications in Combustion and Combustion Diagnostics; (1993) https://doi.org/10.1117/12.145695
Event: OE/LASE'93: Optics, Electro-Optics, and Laser Applications in Scienceand Engineering, 1993, Los Angeles, CA, United States
Single micron-sized spherical particles of carbon and aluminum oxide are suspended in an electrodynamic levitator equipped with a high vacuum system. A CO2 laser is used to heat the particles while their infrared emission signals are monitored from 1.3 - 5.5 micrometers . At atmospheric pressure, particle cooling from air conduction is quite rapid, and the IR signal from a particle follows the 5 millisecond laser pulse. When the levitator is evacuated to pressures ranging from 1 X 10-4 to 1 X 10-5 torr, the efficiency of molecular impact cooling is greatly reduced, and radiative cooling becomes dominant. Under these conditions the particle temperature and emissivity can be found by theoretical fits of the radiative decay curves. For the carbon samples, our analysis has yielded emissivity values in good agreement with those calculated from Mie theory. One interesting feature of this agreement is the determination of emissivities greater than one for the smaller carbon particles. The emissivities found from the thermal decays of Al2O3 micro- particles are much larger than those predicted using Mie theory with bulk optical constants. These anomalously high emissivities for the alumina particles may be caused by surface contaminants.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Dee William Pack, Dee William Pack, Anthony Pluchino, Anthony Pluchino, Donald E. Masturzo, Donald E. Masturzo, "Emissivity measurements of single levitated microparticles", Proc. SPIE 1862, Laser Applications in Combustion and Combustion Diagnostics, (24 May 1993); doi: 10.1117/12.145695; https://doi.org/10.1117/12.145695

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