Overcoming the sensitivity-selectivity trade-off in laser-induced breakdown spectroscopy (LIBS) for uranium isotope analysis via joint spectral decomposition of single- and double-pulse spectra.

Reliable analysis of uranium isotopes (235U and 238U) is essential throughout the nuclear fuel cycle. Laser-induced breakdown spectroscopy (LIBS) has emerged as a promising technique for rapid detection of uranium. However, its application to isotope analysis is hindered by a fundamental sensitivity-selectivity trade-off: High-energy laser pulses, while essential for enhancing sensitivity, exacerbate the overlap between closely spaced spectral features, thereby reducing isotope selectivity. To circumvent this dilemma, the present study proposes a joint spectral decomposition framework that integrates two complementary spectra obtained using single-pulse (SP) and double-pulse (DP) LIBS. SP spectra preserve the narrow spectral features required for isotope discrimination, whereas DP spectra provide enhanced emission intensity and detection sensitivity. By simultaneously fitting the SP and DP spectra under a shared isotope-ratio constraint, the proposed framework combines DP-enhanced sensitivity with SP-derived isotope selectivity, achieving a uranium limit of detection (LOD) of 0.008% in a soil matrix while keeping the isotope-quantification bias within approximately 1 percentage point. These results demonstrate the feasibility of the proposed framework for improving the analytical performance of LIBS-based uranium isotope analysis and provide a basis for further validation toward rapid uranium isotope screening.