Intensity enhancement of AlO molecular bands with 10.6 μm high-repetition-frequency laser irradiation-assisted LIBS

Molecular spectroscopy is critical for the analysis of organic materials and industrial applications. However, laser ablation molecular emission spectroscopy is often limited by poor spectral intensity and stability. To address this issue, this study employs 10.6 μm high-repetition-frequency laser irradiation-assisted laser-induced breakdown spectroscopy (LIBS) to enhance the intensity of molecular spectroscopy. First, the effects of laser power and irradiation time on the intensity and stability of AlO $\left(B^2{\Sigma }^{+}-X^2{\Sigma }^{+},\mathrm{\Delta v}=0\right)$ molecular bands were investigated. The results showed that increasing laser power and irradiation time significantly improved both the spectral intensity and stability. Second, the time-resolved spectra of AlO molecular bands with and without laser irradiation were compared. The results indicated that laser irradiation enhanced the lifetime and emission intensity of AlO molecular bands. Third, by fitting the time-resolved spectral data of AlO molecular bands, the vibrational temperature was calculated, showing a significant increase under laser irradiation. Finally, to further understand the enhancement mechanisms, COMSOL Multiphysics software was used to simulate the ablation morphology of an Al sample at different temperatures, which revealed that the mechanism of spectral enhancement is mainly due to the local thermal effects induced by laser irradiation. These findings collectively demonstrate that 10.6 μm high-repetition-frequency laser irradiation-assisted LIBS is an effective approach to improving the sensitivity of laser ablation molecular emission spectroscopy, offering a novel technological approach for organic material analysis and industrial detection.