Molecular Dynamics Simulation of the Laser Disintegration of Aerosol Particles

Abstract

The mechanisms of disintegration of submicrometer particles irradiated by short laser pulses are studied by a molecular dynamics simulation technique. Simulations at different laser fluences are performed for particles with homogeneous composition and particles with transparent inclusions. Spatially nonuniform deposition of laser energy is found to play a major role in defining the character and the extent of disintegration. The processes that contribute to the disintegration include overheating and explosive decomposition of the illuminated side of the particle, spallation of the backside of large particles, and disruption of the transparent inclusion caused by the relaxation of the laser-induced pressure. The observed mechanisms are related to the nature of the disintegration products and implications of the simulation results for aerosol time-of-flight mass spectrometry are discussed. Application of multiple laser pulses is predicted to be advantageous for efficient mass spectrometry sampling of aerosols with a large size to laser penetration depth ratio.

Photochemical Interaction of Polystyrene Nanospheres with 193 nm Pulsed Laser Light

“…Garrison and co-workers 35 described the UV laser disintegration of aerosol particles using molecular dynamic simulations. Their 2-D simulation of a 110 nm polymer particle irradiated by 337 nm light showed that laser irradiation partially disintegrated the particle and predominantly produced molecules, equivalent to the styrene monomer in this study.…”

Improved sensitivity and mass range in time-of-flight bioaerosol mass spectrometry using an electrostatic ion guide

“…The nature of the ablated material from aerosol particles is dependent on their composition and morphology [16,17]. It has been shown that laser ablation from a particle consisting of an absorbing core surrounded by a nonabsorbing exterior results in an ion plume approximating an exploding sphere [16].…”

“…This is referred to as the total ablation plume model. On the other hand, a strongly absorbing particle of homogeneous composition will result in desorption of material limited to within ϳ10 nm of the particle surface, [6,17], which results in an ion plume directed back toward the ionizing laser. To understand instrument performance from both types of particles, both initial ion plume conditions were considered in this study.…”

“…This was modeled with the direction of the ion ablation assuming a broad cone of solid angle measuring 4.8 radians [2] (Figure 3b) to mimic the findings of Garrison et al [16,17,24] …”

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6)

“…In contrast to mass spectrometers, which use thermal evaporation at temperatures <1000 • C such as the AMS (Canagaratna et al, 2007), even refractory material like mineral dust particles, which are likely to be important IN, can be analyzed. The limitation of this technique is that it is not quantitative because the process of laser ablation is not understood in detail for complex aerosol particles (Schoolcraft et al, 2000). Nevertheless, the importance of different chemical compounds for heterogeneous ice nucleation can be estimated by classifying the ice residue particles into different chemical groups and comparing them to the background aerosol.…”