1 Department of Photonics Engineering, Technical University of Denmark2 Optical Microsensors and Micromaterials, Department of Photonics Engineering, Technical University of Denmark3 National Institute for Laser, Plasma and Radiation Physics4 National Institute for Laser, Plasma and Radiation Physics
The ejection of molecules from a pressed solid target of lysozyme induced by laser ablation in the UV-regime at a wavelength of 355 nm was investigated. The ablation studies were carried out in vacuum at a laser fluence of 2 J/cm2 for which a significant fraction of proteins remains intact. This was verified by matrix-assisted laser desorption ionization (MALDI) spectrometry of thin films deposited on silicon substrates. The deposition rate of lysozyme was found to decrease with the number of shots and was correlated with increasing thermal damage of the lysozyme. This was monitored by measurements of the optical reflectivity of dry lysozyme. The angular distribution of the mass deposition can be fitted well by Anisimov’s hydrodynamic model. The total deposited yield over the entire hemisphere from direct laser ablation of lysozyme was estimated from this model and found to be three orders of magnitude less than the ablated mass.
Applied Physics B, 2013, Vol 113, Issue 3, p. 367-371