拉曼谱学（英文版）

　　I began to recognize the importance of studying Raman intensity as I encountered surface enhanced Raman scattering （SERS） back to 1980's. SERS is a surface phenomenon that as a molecule， especially the nitrogen containing molecule， is adsorbed on the metal surface， in particular the silver electrode， its Raman cross section can be amplified up to a million fold. More interesting is that the Raman mode intensities of the adsorbed molecule are applied voltage dependent. The question then in my mind was： what is the physical picture behind this Raman intensity variation？ In order to solve this issue， we therefore established an algorithm to retrieve the so-called bond polarizabilities from the Raman mode intensities in a systematic way. This leads to a nice harvest， showing that this approach is an adequate direction， albeit the algorithm is semi-classical. This attracted much of my intention in 1980's.During that time， I also thought of the fields of Raman optical activity （ROA） and phase transition. These two fields involve Raman intensity variation as well. In particular， ROA shows that for a chiral molecule under right and left circularly polarized light scatterings， its respective Raman intensities are different， though the difference is very small， only l0-3to 10-4 of its Raman intensity. The differential Raman intensity is called the ROA spectrum.Our work on the phase transitions of the systems with very low degree of doping （ranging from 10-2 to 10-4） seemed to be a success. The rate of mode intensity variation as a function of temperature shows a power law. The exponent of the power law is very sensitive to the doping degree and bears the information of the doping effects.Among the doping effects， the self-similarity by doping which is characterized by the scaling factor， with d the separation between the doping ions and M their mass is most impressive.However， our work on ROA turned out to be a maze， but not a loss. I hence was acquainted with the idea of ROA and proposed a classical formula for predicting the ROA mode signatures. Though with this formula， the prediction was not so successful due to the reason that， at that time， we did not have a clear picture concerning the Raman excited virtual state from the retrieved bond polarizabilities.A clear picture of the Raman excited virtual state sparked us in 2006 when we noticed that the bond polarizabilities retrieved from Raman mode intensities were definitely in variation with the bond electronic densities in the ground state. This hints that bond polarizabilities bear the information of the excited/disturbed charges during the Raman process， i. e.， the electronic structure of the Raman virtual state！ With this breakthrough， we immediately came into the detailed study on the Raman virtual state and extended the bond polarizability algorithm to retrieve the differential bond polarizabilities from ROA mode intensities. All these offered us vivid pictures of the Raman and ROA processes. Though they are classical pictures， just because they are classical， they can provide comprehensive pictures of the Raman virtual state and the phenomena in ROA， which were not known or neglected before. Furthermore， our classical formula for ROA which was developed in 1998， turns out to be a success after its re-interpretation by the bond polarizability. Another byproduct of this work is that we showed， probably for the first time to the best of our knowledge， that there are about 20% electrons in a molecule that are involved in the Raman process. The 14 years' waiting （from 1998 to 2012） is really worthwhile to me！

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