Investigation of Thermal Accommodation Coefficients in Time-Resolved Laser-Induced Incandescence

Accurate particle sizing through time-resolved laser-induced incandescence (TR-LII) requires knowledge of the thermal accommodation coefficient, but the underlying physics of this parameter is poorly understood. If the particle size is known a priori, however, TR-LII data can instead be used to infer the thermal accommodation coefficient. Thermal accommodation coefficients measured between soot and different monatomic and poly-atomic gases show that the accommodation coefficient increases with molecular mass for monatomic gases and is lower for poly-atomic gases. This latter result indicates that surface energy is accommodated preferentially into translational modes over internal modes for these gases.