Micro‐Raman spectroscopy can find the carbon isotopic ratio of CO₂ fluid from the ratio of intensity or area of a ¹³CO₂ peak to that of a ¹²CO₂ peak. We examined the precisions of carbon isotopic ratios (δ¹³C) of CO₂ at constant room temperature and pressure of 10–150 MPa. Measurement of the intensity ratio has precision of 2.8–8.7‰, which is better than that of the area ratio of 4.5–14.7‰. We also investigated the pressure dependence of the Raman intensity ratios and area ratio by changing fluid pressure. When changing fluid pressure from 10 to 150 MPa, the ratios of intensity and area both show negative correlation with fluid pressure (CO₂ density). Pressures of two types affect the Raman spectrum of CO₂ peaks, affecting the peak position and peak shape. To evaluate effects on the peak position, we repeatedly measured the intensity ratio at constant CO₂ pressure (10 MPa) with movement of the grating center position, which is defined as the center value of the analyzed wave number range. Although we moved the grating center position from 1,248.5 to 1,251.5 cm⁻¹, no significant correlation was observed for either ratio of intensity or area. The pressure effect on the ratios can be corrected by ascertaining the CO₂ pressure. Combination with the Raman spectroscopic barometry for CO₂ enables analyses of δ¹³C of CO₂ respectively using the intensity ratio and the area ratio of CO₂ Raman peaks within 8.7 and 14.7‰.

中文翻译：

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显微拉曼质谱对二氧化碳流体碳同位素组成的压力依赖性

微拉曼光谱可以找到CO的碳同位素比₂从强度或一个的面积比流体¹³ CO ₂峰，一个的¹² CO ₂峰。我们检查了碳同位素比率（δ的精度¹³ CO的C）₂在恒定室温和10-150兆帕的压力。强度比的测量精度为2.8-8.7‰，优于面积比的4.5-14.7‰。我们还通过改变流体压力研究了拉曼强度比和面积比对压力的依赖性。当流体压力从10 MPa更改为150 MPa时，强度和面积之比都与流体压力（CO ₂密度）。两种压力会影响CO ₂峰的拉曼光谱，从而影响峰的位置和峰的形状。为了评估对峰位置的影响，我们反复测量了在恒定CO ₂压力（10 MPa）下随着光栅中心位置的移动而产生的强度比，该中心位置被定义为分析波数范围的中心值。尽管我们将光栅中心位置从1,248.5移至1,251.5 cm ^-1，但强度或面积比均未发现显着相关性。可以通过确定CO ₂压力来校正对比率的压力影响。与用于CO拉曼分光气压测定₂使δ的分析¹³ CO的Ç₂分别使用强度比和CO面积比₂的拉曼峰内8.7和14.7‰。