Picosecond Laser Ablative Mass Spectrometry of Metallic Targets

Laser ablative mass spectrometry was used to study the molecular fragments produced due to picosecond laser ablation of metallic targets under vacuum conditions (~10^-5 Torr). Mass spectrometer used is a residual gas analyzer (RGA300) with 3 or 8eV ion energy, operating in first stability zone. Fundamental wavelength from Nd:YAG laser (1064nm) delivering 30ps pulses with 10Hz repetition rate and energy varied between 5-45mJ was observed to affect the ablation of target, resulting in enhanced plasma plume expansion along with the decomposition mechanism of target, which is measured in terms of partial pressures by RGA. The experimental setup was also used to study the plasma plume evolution. To understand the hydrodynamics of the ablated mass, one dimensional radiation hydrodynamic(1D-RHD) studies using modified MULTI-fs code was performed. Multiphoton ionization was incorporated into the code. The simulated plasma properties such as temperature and electron density were experimentally corroborated using LIBS data obtained from the same experimental setup. This work aims at establishing a relation between the plasma plume properties and mass spectrum which eventually can be used for the study of reaction pathways.