A novel method for fast and robust calculation of Boltzmann plots from molecular spectra is presented. Its use is demonstrated on the OH(A-X) spectrum near 310 nm. A limitation of the method is identified: for overlapping spectra of the OH(A-X) and N2(C-B, Δv = 1) band sequence, the calculation may often fail due to insufficient number of measured points. This is solved by introducing experimentally determined bounds for the N2(C) rotational distribution. Three cases are presented: (i) with undisturbed OH(A-X) emission, (ii) with strong emission of N2(C-B) in the said spectral range, and (iii) with weak but not negligible nitrogen emission. In case (ii), the data in the spectral range 306-320 nm are sufficient for the analysis. In case (iii), information from another spectral range with undisturbed N2(C-B) emission is necessary. These illustrate all relevant cases often encountered in laboratory plasmas. The calculated Boltzmann plots are not further analyzed in this article but can be used for development and validation of kinetic models with rotational resolution. The implementation of the reported method using the massiveOES software package written in the Python language is available in the supplementary material.

中文翻译：

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从重叠的分子光谱中推导出旋转量子态分布

提出了一种从分子光谱快速、稳健地计算玻尔兹曼图的新方法。它的使用在 310 nm 附近的 OH(AX) 光谱上得到了证明。确定了该方法的局限性：对于 OH(AX) 和 N2(CB, Δv = 1) 波段序列的重叠光谱，由于测量点数量不足，计算可能经常失败。这是通过为 N2(C) 旋转分布引入实验确定的界限来解决的。提出了三种情况：（i）具有未受干扰的 OH（AX）发射，（ii）在所述光谱范围内具有强烈的 N2（CB）发射，以及（iii）具有微弱但不可忽略的氮发射。在情况 (ii) 中，306-320 nm 光谱范围内的数据足以进行分析。在情况 (iii) 中，需要来自具有未受干扰的 N2(CB) 发射的另一个光谱范围的信息。这些说明了实验室等离子体中经常遇到的所有相关案例。本文不会进一步分析计算出的 Boltzmann 图，但可用于开发和验证具有旋转分辨率的动力学模型。使用 Python 语言编写的 massOES 软件包实现报告的方法可在补充材料中找到。