Plume Analysis in Laser Desorption and Ablation : Basics for Ambient Ionization

The fundamental physical processes of mid infrared laser ablation in the context of laser desorption mass spectrometry were investigated. Understanding the mechanisms of infrared laser desorption and ablation can lead to improvements in these techniques and expand their applications. Particles were generated from glycerol irradiated at atmospheric pressure using a tunable infrared laser at wavelengths between 2.6 and 3.8 m. The wavelength dependence of size distributions of ablated particles was measured. In addition to particle sizing, fast photography was used to study the dynamics of mid infrared laser desorption and ablation. The wavelength and energy of the infrared laser can be used to effectively "tune" the composition of the desorption plume. This ability to control the composition of the plume will be used in the development of IR laser ambient ionization mass spectrometry techniques such as atmospheric pressure matrix-assisted laser desorption ionization (AP-MALDI) and matrix-assisted laser desorption electrospray ionization (MALDESI) where the ability to control material removal is critical to efficient ionization.