Effect of background gas, sample angle and laser polarization on the enhancement effect of resonant laser ablation

Abstract

The main characteristic of the resonant laser ablation (RLA) phenomenon is an enhancement in the number of atoms ablated from the surface when the ablation laser wavelength is tuned to match a gas phase transition of the analyte of interest. It has been suggested in the literature that the RLA phenomenon is probably based on radiation trapping with contributions from desorption induced by electronic transitions. In the present paper, a study was made of the effects of laser polarization, sample angle and the identity of the background gas on the enhancements observed during resonant laser ablation. The effects of laser polarization and of sample angle relative to the laser beam were observed to be wavelength-independent at low incident laser powers. The rate of resonant ablation under an argon atmosphere was found to be twice the ablation rate under helium, while the use of a nitrogen atmosphere reduced the ablation rate by a factor of ten compared with argon, and effectively removed the wavelength dependence from the experiment. The results indicated that the magnitude of the RLA-enhanced desorption could be optimized with respect to the incident angle and the polarization of the incident laser, and by ablation under an argon atmosphere.