AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Comparison of Nanosecond and Femtosecond Laser Ablation in Single Particle Mass Spectrometry
RAMAKRISHNA RAMISETTY, Ahmed AbdElMonem, Xiaoli Shen, Harald Saathoff, Thomas Leisner, Claudia Mohr, Karlsruhe Institute of Technology
Abstract Number: 293 Working Group: Single Aerosol Particle Studies - Techniques and Instrumentation
Abstract Single particle mass spectrometry is a valuable technique for the analysis of size, composition, and mixing state of individual aerosol particles. Laser ablation is the dominant method for desorption and ionization of the particles. Due to their relatively high power, UV wavelength, and good trigger options, excimer lasers are often used to realize desorption and ionization in one single step. With the advent of high-energy, ultra-short pulse lasers, i.e. femtosecond (fs) laser ablation allows for precise removal of material with high spatial and depth resolution. Ultra-short pulses are less thermal diffuse and cause less collateral damage than longer pulses.
In this work we use the laser ablation aerosol time-of-flight single particle mass spectrometer LAAPTOF (Aeromegt GmbH), originally equipped with a 193 nm excimer laser. This work will discuss mass spectra from the original excimer laser LAAPTOF in comparison with spectra from the same instrument coupled to an fs-laser with similar pulse energy but longer wavelengths. Since triggering of typical fs-lasers is hard to realize, some technical changes were applied allowing the acquisition of mass spectra with hit rates comparable to the original set up. Differences in the mass spectra observed for single size particles of polystyrene, SiO$_(2), NH$_(4)NO$_(3), NaCl, and custom made core shell particles will be discussed for different focus positions of the laser, for different laser power, and also for different wavelengths.