[Raman spectra of carbonate ions as pressure gauge at high pressure and room temperature].

Three aqueous solutions of sodium carbonate (1.5, 2.0 and 2.5 mol x 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 v1 066. The experiment was conducted from 0 to 1.7 GPa under quasihydrostatic conditions at temperature of 22 degrees C. 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 ofthe v1 066 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 v1 066 peak. Besides, the data fitting generated the formula: p/MPa = 174.13deltavl 066/cm(-1) -59.03 (deltav1 066 = v1 066 -v(0)1 066, where v(0)1 066 denotes the Raman shift of v1 006 peak of carbonate ion under the ambient pressure, which can be used as a pressure gauge in pure Na2CO3 solution.