常温高压下碳酸根离子的拉曼谱峰标定压力初探

Raman Spectra of Carbonate Ions as Pressure Gauge at High Pressure and Room Temperature

在准静水压的条件下，利用碳化硅压腔和显微拉曼光谱原位测量技术，在0～1．7GPa压力范围测定22℃高压下三种不同的H2O-Na2CO3体系（1．5，2．0，2．5mol·L^-1）中CO3^2-的对称伸缩振动v1066拉曼谱峰的变化。结果表明，在室温条件下，碳酸根的v1066峰的拉曼位移随着压力的增大而线性增加。三种浓度下v1066峰的拉曼位移与压力的拟合直线彼此接近，斜率误差小于1％，偏差小于系统误差，因此在实验误差范围内碳酸根浓度对v1066峰随压力变化的行为不存在影响。经过数据拟合得到公式：p／MPa=174．13△v1066／cm^-1-59．03（△v1066=v1066-v1066^0,v1066^0。为体系零压时碳酸根离子v1066峰的拉曼位移）。此公式可以用于常温下在含有纯碳酸钠体系中的压力标定。

Three aqueous solutions of sodium carbonate （1.5, 2.0 and 2.5 mol · L^-1 ） were studied by in-situ Raman spectrum in a moissanite anvil cell in order to measure the Raman shift of symmetric stretching vibration of carbonate ion at around v1066. The experiment was conducted from 0 to 1.7 GPa under quasihydrostatie conditions at temperature of 22℃ The result showed that the increase in Raman wavenumber shift of in-plane bending vibration of carbonate ion is linearly proportional to the rise of pressure under room temperature. At the three concentrations mentioned above, the correlations between Raman shift of the v1066 peak and the pressure are depicted as three nearly identical curves, with a slope error smaller than 1%. The deviation, being smaller than the systemic error, suggested that the concentration of carbonate ions, within experimental errors, has no detectable influence on the pressure-induced shift of v1066 peak. Besides, the data fitting generated the formula： p/MPa=174.13△v1066/cm^-1-59.03（△v1066=v1066-v1066^0, where v1066 denotes the Raman shift of v1066 peak of carbonate ion under the ambient pressure, which can be used as a pressure gauge in pure Na2CO3 solution.