## 3 Results
### Correlation Between LIBS Physical Parameters and Ablation Morphology Parameters  
(a) Quantitative Analysis of the Influence of Crater Morphology  
To systematically investigate the influence of ablation morphology on LIBS signal intensity, several cutting tool alloy samples were analyzed under single-pulse laser excitation at varying fluences. Post-ablation, the crater morphology was quantitatively characterized via high-resolution 3D surface profilometry. Key morphological descriptors, including the crater diameter (D), surface roughness (Ra), and crater volume (V), were extracted from each ablation site.  
Simultaneously, the emission intensity of Co I at 340.512 nm was recorded for each corresponding pulse. The results revealed a strong correlation between morphological features and LIBS signal intensity, as shown in Figure 12a. In particular, both crater volume and surface roughness exhibited positive linear trends with spectral intensity, suggesting that enhanced material removal and plasma-surface coupling contribute to increased emission efficiency, which is shown in Figure 12b.  
These findings demonstrate that morphological variation introduces significant signal bias, independent of elemental concentration, and thus represent a quantifiable manifestation of the matrix effect. Incorporating such morphological parameters into calibration  
Figure 11: Three-dimensional reconstruction of the ablation surface. (**a**) All-in-focus image created by merging a sequence of defocused images through focus measurement. (**b**) Pseudo-colored depth map depicting the 3D structure of the ablation crater.  
Figure 12: Influence of Ablation Morphology on Cobalt (Co I) Emission Intensity in LIBS Analysis. (**a**) Emission intensities of the Co I spectral line at 340.512 nm from cutting tool alloy samples with identical Cobalt concentrations, illustrating signal variability induced by morphological differences in the ablation craters. (**b**) Scatter plot of Co I emission intensity versus ablation crater depth, revealing a nonlinear relationship characterized by a peak emission at an intermediate depth and reduced intensities at both shallower and deeper ablation levels.  
models is therefore critical for improving the analytical accuracy and robustness of LIBS measurements. The Co I (340.512 nm) line intensity exhibited substantial variability among samples possessing identical Co concentrations, underscoring the influence of factors beyond elemental abundance. A scatter plot of crater depth versus Co I intensity revealed a nonlinear relationship, with the maximum emission observed at an intermediate crater depth. Both linear and second-order polynomial models were applied to fit the data. The polynomial model provided the best description of the observed trend, yielding a coefficient of determination of R\({}^{2}\) = 0.89, indicative of a strong correlation between crater depth and spectral response. These findings support the hypothesis that ablation morphology acts as a secondary modulator of LIBS intensity, contributing to signal variation even in the absence of compositional changes.  
Morphology-induced spectral deviation  
As shown in Table 2, Samples A and B had comparable Co concentrations (wt%), yet their LIBS signal intensities differed by 23.6%. Confocal laser scanning microscopy (CLSM) analysis revealed that Sample B had significantly greater crater depth and increased post-ablation surface roughness, indicating that surface morphology substantially influences the variation in Co LIBS signals.