Group Theory Analysis Of SO₄^2- And CO₃^2- Raman Spectrum

SO42- and C032- are major anions in seawater. which are integral part of many mineral. Their signal shows important geochemical information and represents the characteristics of the underground mineralization and to some extent reflects the deep seabed geological processes that occur and the mineralization process. Therefore, the study of SO42- and CO32 has great significance to the origin and evolution of hydrothermal fluids and the whole process of geological mineralization.In this thesis, symmetry analysis, infrared and Raman active judgment. vibration frequency calculations were obtained up on group theory. The results are as follows:the structure of SO42- belongs to Td point group, which has 9 vibration modes. they are one A1 vibration mode,one E vibration mode and two triple degenerate T2 vibration modes, all of them are Raman active. SO42- has 4 fundamental vibrations, which are v1=979.83cm-1 v3=475.76 cm-1, v4=1077.34 cm-1, v2=579.87 cm-1. Symmetric stretching vibration frequency v1 is determined by K and F, v1 increases with the increase of K and F bending vibration frequency v2 is determined by the H and F, v2 increases with the increase of H and F; asymmetric stretching vibration frequency v3 and distorted frequency v4 are determined by K,H and F. The structure of CO32- belongs to D3h point group, which has 6 fundamental vibration modes, they are one vibration mode,one A2 vibration mode and two double degenerate E vibration modes, A1 and E are Raman active. CO32- has 4 fundamental vibrations, which are v1=1059.95 cm-1 , v3=1414.94 cm-1, v4=679.97 cm-1. Symmetric stretching vibration frequency v1, is determined by K and F, v1 increases with the increase of K and F:asymmetric stretching vibration frequency v3 and distorted frequency v4 are determined by K,H and FThe thesis also obtained Raman spectrum and simulated Raman spectrum of SO42- and CO32- by Laser Raman spectroscopic system and Gaussian03 software. From SOa2 experimental Raman spectra we can observe SO symmetric stretching (v1) locates at 981cm-1, SO asymmetric stretching (v3) locates at 1106 cm-1, SO distorted stretching (v4) locates at 617 cm-1, but SO bending stretching (v2) is too weak to observe:From CO32-experimental Raman spectra we can observe CO symmetric stretching (v1) locates at 1066 cm-1, the other two peaks are too weak to observe. Gaussian software simulation result of SO42- is:v1 locates at 1008.3cm-1, v3 locates at 1138.1cm-1. v4 locates at 460.0cm-1. v2 locates at 647.5cm-1; The simulation result of CO32- is v1 locates at 1131.5cm-1, v3 locates at 1489.4cm-1, v4 locates at 718.9cm-1. Experimental and simulation complement each other to verify the accuracy of the results of group theory.