HR: 0830h
AN: A11E-0032    [PDF]
TI: The Potential for Quantitative Atmospheric Black Carbon Measurements Using Laser-Induced Incandescence (LII)
AU: * Michelsen, H A
EM: hamiche@ca.sandia.gov
AF: Sandia National Labs, MS 9055 P. O. Box 969, Livermore, CA 94551 United States
AU: Gershenzon, M Y
EM: mygersh@ca.sandia.gov
AF: Sandia National Labs, MS 9055 P. O. Box 969, Livermore, CA 94551 United States
AU: Witze, P O
EM: witze@sandia.gov
AF: Sandia National Labs, MS 9055 P. O. Box 969, Livermore, CA 94551 United States
AB: Laser-induced incandescence (LII) has been used extensively to make qualitative observations of soot temporal and spatial distributions in engines, engine exhaust, and flames. LII detection involves heating particles with a laser and measuring the resulting blackbody emission. Recent work has been aimed at implementing this technique quantitatively for soot volume fraction measurements and particle sizing. It appears to be sensitive to parameters, such as ambient temperature and pressure, laser beam spatial and temporal profile, gate width and delay, and particle composition, and its applicability under a wide range of conditions has not been demonstrated. We have performed experiments to identify the influence of measurement conditions and developed a model of the LII process that accounts for particle heating by laser absorption, oxidation, and annealing and cooling by sublimation, radiation, and conduction to the surrounding atmosphere. The model also accounts for mass loss by oxidation, sublimation, and nonthermal photodesorption of carbon clusters. The results of this study allow us to identify the largest uncertainties associated with the understanding of LII and predict the influence of measurement parameters on LII signal under varying conditions encountered in the atmosphere.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting