Enhancement of Hyper-Raman Scattering Intensity

The hyper-Raman scattering cross section is extremely small, typically of the order of 10 cm per molecule [24]. Therefore, an enhancement of signal intensity is essential in order to utilize this phenomenon as a practical spectroscopic tool in the field of molecular science. In a similar marmer to the enhancement of Raman scattering 

The numbers of IR- and Raman-active modes are 4 (4tiJ and 10 (2ag + 8hg), respectively. On the other hand, hyper-Raman-active modes are all of the modes with u symmetry, including the silent modes. Compared with the theoretically calculated result, the expected modes are clearly seen in the spectmm. (The appearance of Raman-active modes is due to magnetic dipole contributions.) 

Ina similarmarmerto surface-enhanced Raman scattering, surface-enhancement of hyper-Raman scattering is a promising method to study adsorbed molecules on metal surfaces [24]. Based on recent developments in plasmonics, design and fabrication of metal substrates with high enhancement activities is now becoming possible [21]. Combination of the surface enhancement with the electronic resonances would also be helpful for the practical use of hyper-Raman spectroscopy. Development of enhanced hyper-Raman spectroscopy is awaited for the study of solid/liquid interfaces. 

The background of hyper-Raman scattering has been described and several enhancement mechanisms presented. Unique features of hyper-Raman scattering have been demonstrated for Ceo- 

Here we have described two second-order non-linear spectroscopies, SFG in detail and hyper-Raman scattering briefly. 

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