Development of a Li molecular removal method for minimizing interference in radiocarbon (14C) measurements using laser technology

Mass interference of Li molecular ions (Li 2 ) in accelerator mass spectrometry (AMS), which uses an even number of positive ion in the high-energy part, sometimes presents challenges in accurate radioactive carbon ( 14 C) measurements. The presence of these molecular ions, which share the same mass-to-charge ratio as 14 C, leads to errors that undermine the reliability of AMS measurements. In this work, we propose and validate a new laser-based method for selectively removing Li 2 ions. A fiber-optic laser with 1.166 eV photon energy, which is an energy higher than the binding energy of Li 2 anion electrons while at such low energy that it does not affect the electrons of 14 C anion, effectively separates only the electrons of Li 2 anion. The method reduced the Li 2 signal by 94.3 %, maintaining the integrity of the 14 C measurement. Our findings indicate that laser technology can significantly improve the AMS sensitivity and reliability for 14 C analysis, which can be a useful tool for various scientific applications.