The potential energy curves of the ground and first exicted states were calculated by CCSD(T) and MRCI methods. Effects of the core-valence correlation and relativistic corrections on the the potential energy curves are included in present calculation. To obtain reliable results, the Davidson modification (MRCI+Q) which is compensate for the high order truncation is also considered in present calculation. Furthermore, in order to avoid the basis set superposition error, the complete basis set limit extrapolation is also included in present calculation. With these potential energy curves, the spectroscopic parameters are determined and compared with available theoretical and experimental studies. The result indicated that present results are in good agreement with experimental data and the core-valence correlation correction has larger effects on the spectroscopic constants than relativistic correction.
Proc. SPIE. 9685, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; and Smart Structures and Materials
Surface-Enhanced Raman Scattering (SERS) is a powerful spectroscopic technique for highly sensitive molecular detection. It effectively improves the defect of low sensitivity of normal Raman spectra. So it is widely used in the area of surface science, analytical science, biological science and so on. Using Density Functional Theory (DFT) and Time- Dependent density functional theory (TD-DFT), the SERS spectrum has been simulated for biphenyl l-4, 4′-dithiol (BPDT, HS-(C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>-SH), p-terphenyl-4, 4″-dithiol (TPDT, HS - (C<sub>6</sub>H<sub>4</sub>)<sub>3</sub>-SH )1, 4-benzenedithiol (BDT) absorbed on AuNPs and AgNPs. The SERS which aroused by C-C stretching mode is increasing with the benzene ring. Whereas, for the SERS of S-H bending vibrational mode, changing the position of S atom have little effect. The C-S stretching mode and S-H stretching mode are also little effect by the insert number.