Plasma emission during time-resolved laser-induced incandescence measurements of aerosolized metal nanoparticles

There has been speculation that several commonly observed anomalies in time-resolved laser-induced incandescence (TiRe-LII) measurement data may be caused by bremsstrahlung emission from a laser-induced plasma, a phenomenon known to occur at higher fluences typical of laser-induced breakdown spectroscopy. This paper presents the first theoretical framework to investigate a laser-induced plasma formation under LII measurement conditions, and explores how this plasma may affect time-resolved spectral intensity measurements. At fluences greater than 0.8 J/cm2, the absorption cross-section of the laser-energized nanoparticle is enhanced due to inverse bremsstrahlung absorption, and bremsstrahlung emission results in an overestimation of the nanoparticle temperature due to the corruption of the incandescence signal. Under these conditions, neutral bremsstrahlung emission is more prevalent than electron–ion bremsstrahlung due to the weak nature of the induced plasma. Nevertheless, the current model does not predict laser-induced plasma phenomena below ~ 0.5 J/cm2, typical of low-fluence TiRe-LII measurements.