Self-absorption of spectral lines is known to lower the performance of analytical measurements via calibration-free laser-induced breakdown spectroscopy. However, the error growth due to this effect is not clearly assessed.

Here we propose a method to quantify the measurement error due to self-absorption based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium. Validated through spectroscopic measurements for a binary alloy thin film of compositional gradient, the method evidences that measurement performance lowering due to self-absorption depends on the spectral shape of the analytical transition and on the intensity measurement method. Thus, line-integrated intensity measurements of Stark broadened lines enable accurate analysis, even at large optical thickness, if line width and plasma size are precisely known. The error growth due to self-absorption is significantly larger for line shapes dominated by Doppler broadening and for line-center intensity measurements. The findings present a significant advance in compositional measurements via calibration-free laser-induced breakdown spectroscopy, as they enable straightforward selection of most appropriate analytical lines.

已知谱线的自吸收会通过免校准激光诱导击穿光谱降低分析测量的性能。然而，由于这种效应导致的误差增长没有得到明确评估。

在这里，我们提出了一种方法来量化由于自吸收引起的测量误差，该方法基于局部热力学平衡中等离子体光谱辐射的计算。通过对成分梯度的二元合金薄膜的光谱测量进行验证，该方法证明由于自吸收导致的测量性能降低取决于分析跃迁的光谱形状和强度测量方法。因此，如果精确知道线宽和等离子体尺寸，斯塔克加宽线的线积分强度测量可以实现准确分析，即使在较大的光学厚度下也是如此。对于以多普勒展宽为主的线形和线中心强度测量，由于自吸收导致的误差增长明显更大。