Raman spectroscopy can be used to determine density of gases, because the energy of fundamental vibrational modes is affected by intermolecular distances. The key problem is the estimation of exact peak positions of Raman bands, because the analyses require a precision that is mostly less than the pixel resolution of modern Raman spectrometers. A new method to determine peak positions of Raman bands and atomic emission lines in a discontinuous spectrum without numerical manipulations is tested in this study: modified scanning multichannel technique. Relocation of the gratings with a Sinus Arm Drive can be performed over a distance that is only a fraction of the pixel size that allows peak position estimations with precisions smaller than the pixel resolution and to determine the uncertainty in this estimation. This uncertainty was not determined in previous studies about gas densimeters, resulting in a large variety of inconsistent data. The new method is tested with fluid inclusions in quartz. A CO₂ density of 0.1477 ± 0.0006 g·cm⁻³ and 0.8880 ± 0.0007 g·cm⁻³ determined with microthermometry correspond to a Fermi dyad of 103.12 ± 0.27 cm⁻¹ and 104.71 ± 0.26 cm⁻¹. A CH₄ density of 0.3461 ± 0.0002 g·cm⁻³ and 0.4011 ± 0.0001 g·cm⁻³ correspond to peak positions of 2910.66 ± 0.12 cm⁻¹ and 2910.57 ± 0.12 cm⁻¹. The error in these numbers must be regarded as the best estimated uncertainties of peak positions, which are probably slightly adjusted to higher values due to mechanical irregularities of the Sinus Arm Drive in modern Raman systems.

中文翻译：

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拉曼光谱气体密度计的完善

拉曼光谱可用于确定气体密度，因为基本振动模式的能量受分子间距离的影响。关键问题是拉曼谱带精确峰值位置的估计，因为分析需要的精度大多低于现代拉曼光谱仪的像素分辨率。本研究测试了一种无需数值操作即可确定不连续光谱中拉曼谱带和原子发射线峰值位置的新方法：改进的扫描多通道技术。使用 Sinus Arm Drive 重新定位光栅的距离仅为像素大小的一小部分，这允许以小于像素分辨率的精度进行峰值位置估计，并确定该估计中的不确定性。这种不确定性在之前关于气体密度计的研究中没有确定，导致了大量不一致的数据。用石英中的流体包裹体对新方法进行了测试。一员₂密度为0.1477 ± 0.0006 g·cm ^-3和0.8880 ± 0.0007 g·cm ^-3对应于103.12 ± 0.27 cm ^-1和104.71 ± 0.26 cm ^-1的费米二元组。0.3461 ± 0.0002 g·cm ^-3和0.4011 ± 0.0001 g·cm ^-3的CH ₄密度对应于2910.66 ± 0.12 cm ^-1和2910.57 ± 0.12 cm ^{-1 的}峰位置。这些数字中的误差必须被视为峰值位置的最佳估计不确定性，由于现代拉曼系统中 Sinus Arm Drive 的机械不规则性，可能会稍微调整为更高的值。