Observations and analysis of resonant laser ablation of GaAs

Laser ablation of solid GaAs samples has been studied using one tunable pulsed dye laser. At relatively low laser power, enhancements of up to several hundred times have been observed in the yield of resonantly ionised Ga using laser wavelengths corresponding to the atomic transition 4²P_1/2-4²D_3/2. The influences of laser power and target geometry, on the ion yield and spectral profile, are discussed. It is argued that the resonant excitation and ionisation processes occur in the gas phase of the atoms ablated from the sample surface, and the observed asymmetric spectral profile results from laser-induced collisional processes, e.g., optical collisions, under conditions of relatively high atomic density in the interaction region. Potential applications are foreseen for resonant laser ablation in trace analysis.