As an optical analogue to 2D NMR, doubly vibrationally enhanced (DOVE) four wave mixing spectroscopy involves two infrared transitions and a Raman transition. The magnitude of the DOVE second hyperpolarizability γ can be theoretically estimated if the values of the dipolar moments of the two infrared transitions and the γ of the Raman transition are known. The Raman γ can be measured by using four wave mixing interferometric method or conventional Raman spectroscopy in the presence of an internal standard. Here, we have demonstrated that the second hyperpolarizability γ of a selected vibrational mode of a molecule can be determined by using the computational Raman activity against an internal standard with a known Raman γ value. This approach provides a convenient way for prediction of the γ magnitude of DOVE four wave mixing spectroscopy. By using the Hartree-Fock (HF) method, the DFT method, and the MP2 method, our work covers from the less anharmonic region &lt;2000 cm<sup>-1</sup> to the more anharmonic region &gt;2000 cm<sup>-1</sup> covering C-H, C-D and C≡N stretching modes of benzene, deuterated benzene, acetonitrile, deuterated acetonitrile, and tetrahydrofuran. By choosing a suitable method and basis set, this facile approach could be applied to a broader spectral range for Raman γ estimation of various materials. Further work is extended to estimate the magnitude of the DOVE second hyperpolarizability of some of the listed samples involving C-H vibrations and identify the strong DOVE signatures for label-free molecular determination in a complex system.

Determination of second hyperpolarizability with computational Raman activities and identification of DOVE signatures for selected molecules

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.