Raman imaging is an emerging tool for the analysis of meteorites, as it is capable of describing mineralogy, carbon composition/speciation, and crystal orientation all within a petrographic context. Adequately examining the heterogeneous composition of a meteorite often requires long image collection times on the timescale of days. However, the wavenumber calibration of the Raman spectrometer drifts over long timescales resulting in low wavenumber precision for the Raman spectra comprising a large Raman image. This decrease in wavenumber precision can compromise the analysis of geological markers that can provide important information on a meteorite sample. We examine, in detail, the change in bandwidth and wavenumber of the Raman bands and Hg–Ar emission lines in our Raman images as a function of time and laboratory temperature. To overcome the drift in calibration, we utilize a commercial WITec Raman instrument with a built‐in Hg–Ar calibration lamp to individually calibrate each spectrum in the Raman image. We show that using the Hg–Ar calibration, we can improve the wavenumber precision for the spectra in our Raman images from ~±0.15 to ~±0.05 cm⁻¹ for Raman spectra collected over multiple days. This is important as it improves measurements of mineral chemistry, latent strain, and other features that are dependent upon accurate peak position determination. We also examine the spectral signal‐to‐noise ratio needed to minimize the wavenumber error when fitting bands to Gaussian/Lorentzian profiles. We then use our results to suggest a general method for calibrating the wavenumber of Raman spectra in large Raman images.

中文翻译：

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使用汞氩灯校准大拉曼图像中的拉曼波数

拉曼成像是一种新兴的陨石分析工具，因为它能够在岩石学背景下描述矿物学，碳组成/形态和晶体取向。充分检查陨石的异质成分通常需要几天的时间，因此图像采集时间较长。然而，拉曼光谱仪的波数校准在较长的时间尺度上漂移，从而导致包括大拉曼图像的拉曼光谱的波数精度较低。波数精度的这种下降会损害对可以在陨石样品上提供重要信息的地质标志物的分析。我们详细研究了拉曼图像中拉曼能带和Hg-Ar发射谱线的带宽和波数随时间和实验室温度的变化。为了克服校准中的漂移，我们使用了带有内置Hg-Ar校准灯的商业WITec拉曼仪器来分别校准拉曼图像中的每个光谱。我们表明，使用Hg–Ar校准，可以将拉曼图像中光谱的波数精度从〜±0.15 cm提高到〜±0.05 cm^-1表示在多天内收集的拉曼光谱。这一点很重要，因为它可以改善矿物化学，潜在应变和其他取决于精确峰位置确定的特征的测量。我们还研究了在将频带拟合到高斯/洛伦兹曲线时将波数误差最小化所需的频谱信噪比。然后，我们使用我们的结果来建议一种用于校准大拉曼图像中拉曼光谱波数的通用方法。