Machine learning coupled laser-induced breakdown self-reversal isotopic spectrometry for determining lithium isotope concentration

Laser-induced breakdown self-reversal isotopic spectrometry (LIBRIS) is implemented to record the Li 670.8 nm peak self-reversal shift with varying ⁶Li atom percent compared to ⁷Li. The self-reversed peak center wavelength is shown to shift across a range of 13.813±1.21pm in LiOH⋅H₂O⁶Li samples varying from 3 to 95 ⁶Li atom percent. Supervised machine-learning regressions are trained on the self-reversal shift in order to quantify the isotopic concentration of the samples. A stacked ensemble model using multiple supervised regression base learners is found to yield the superlative characterization of isotopic content with an <i>RMSE</i> of 5.66 at.% and a detection limit of 18.8 at.%.