Aerosol-particle sizes from light emission during excitation by TEA CO2 laser pulses

Abstract

Preliminary measurements of the time-dependent light emission from aerosol particles (generated from submicron powders of carbon black and alumina) during excitation with pulses from a TEA CO2 laser show that this emission may be simply related to particle size.

Characterizing elemental, equivalent black, and refractory black carbon aerosol particles: a review of techniques, their limitations and uncertainties

“…Interference during Raman spectroscopy measurements motivated the earliest LII work on rBC produced in flames [ 198 ]. Weeks and Duley [ 199 ] showed that LII signals could be related to particle size for carbon black; however, it was the subsequent theoretical and observational studies [ 200 , 201 ] that showed that LII could be used to directly derive the rBC properties in flames. For example, Melton [ 200 ] showed that the magnitude of the incandescence signal could be related to the volume concentration of rBC in the measurement region.…”

Modeling laser-induced incandescence of soot: a summary and comparison of LII models

“…The (a)s p ecific heat (Table 1) and (b) density (Table 1) of the particle and (c) heatcapacity ratio of the surrounding gases (Table 4) are shown as a function of temperature. Values used in the different models are indicated in the legend in each panel perature and thus exclude the third term in (15). There is currently some debate in the community about whether (2) or (15) is the correct expression to use.…”

Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

“…The principle of LII is to rapidly heat the nano-sized soot particles by thermally energizing them (using a pulsed laser beam of nano-second duration) to temperatures significantly higher than the temperature of the investigated medium and to measure the resulting incandescence signal interpreted as thermal emissions based on the Planck law. Since the discovery of the LII phenomenon [2,3] and the recognition that it can be used as a soot diagnostics [4], LII has been developed into a powerful and versatile soot diagnostic technique and continuously improved. For example, the two-color LII technique (2C-LII), in which the incandescence signal is detected at two wavelengths in the visible spectrum, has been demonstrated to be superior to the conventional onecolor LII technique, since it provides information of the particle temperature during the LII process and does not require calibration against a source of known particle concentration [5,6].…”