Asymmetric environment around the thiourea molecule in aqueous solution as evidenced by the bond polarizability derivatives from Raman intensity

By UV Raman scattering and an algorithm developed by Wu et al. [B. Tian, G. Wu, G. Lu, J. Chem. Phys. 87 (1987) 7300], we demonstrated that for thiourea (TU) aqueous solution with TU concentration larger than 0.05 M, the polarizability derivatives of the two C-N stretches of the TU molecule are not equivalent. This is interpreted in that within the time scale of subpicosecond which is the duration of the Raman scattering, the instantaneous environment (potential field) around a TU molecule is not symmetric with respect to the mirror image along the S-C bond and vertical to the S-C-N2 skeleton. This is a dynamical symmetry breaking. Another possibility is that there is asymmetric structural formation of the environment around a TU molecule due to hydrogen bonding in the TU concentric solution.