Resonance enhancement of ion signals in direct isotope analysis of metal samples by adopting 2-color resonant laser ablation mass spectrometry

The enhancement of ion signals by the resonant laser ablation (RLA) process was investigated by using a 2-color RLA mass spectrometry for samples containing Pb and Ni. Two laser beams, a second harmonic of Nd:YAG laser (532 nm) and a UV beam of frequency tunable dye laser, were used for either simultaneous ablation by directing both lasers to the target sample or laser ablation followed by a resonant ionization. In both cases, the resonant enhancement of the ion signal was observed, but the mass resolution was much better when two lasers contribute to the laser ablation process by arranging both beams hit the sample at the same position. The enhancement factor was more prominent when the laser power was kept at low. The maximum resonance enhancement was more than 160 times for the Pb case when compared to the non-resonant laser ablation. Several NIST standard reference materials were analyzed by adopting RLA.