Significant Contributions of the Albrecht鈥檚 A Term to Nonresonant Raman Scattering Processes

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• 作者：Zu-Yong Gong ; Guangjun Tian ; Sai Duan ; Yi Luo
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2015
• 出版时间：November 10, 2015
• 年：2015
• 卷：11
• 期：11
• 页码：5385-5390
• 全文大小：330K
• ISSN：1549-9626

文摘

The Raman intensity can be well described by the famous Albrecht鈥檚 Raman theory that consists of A and B terms. It is well-known that the contribution from Albrecht鈥檚 A term can be neglected without any loss of accuracy for far-off resonant Raman scattering processes. However, as demonstrated in this study, we have found that this widely accepted long-standing assumption fails drastically for totally symmetric vibration modes of molecules in general off-resonant Raman scattering. Perturbed first-principles calculations for water molecule show that strong constructive interference between the A and B terms occurs for the Raman intensity of the symmetric O鈥揌 stretching mode, which can account for 鈭?0% of the total intensity. Meanwhile, a minor destructive interference is found for the angle bending mode. The state-to-state mapping between Albrecht鈥檚 theory and perturbation theory allows us to verify the accuracy of the widely employed perturbation method for the dynamic/resonant Raman intensities. The model calculations rationalized from water molecule with the bending mode show that the perturbation method is a good approximation only when the absolute energy difference between the first excited state and the incident light is more than five times greater than the vibrational energy in the ground state.