Chapter 2 - Frontiers of Linear and Non-Linear Raman Spectroscopy: From a Molecule to a Living Cell

Abstract

Raman spectroscopy is continuously growing and since 1928 seems to have reached a new horizon. This chapter briefly overviews the recent advances in the laboratory of applications of linear and nonlinear Raman spectroscopy. It describes ultrafast chemical exchange dynamics of reaction intermediates as investigated by the band shape analysis of linear Raman spectra. Its application now extends over all basic sciences including physics, chemistry, and biology as well as various research fields in industrial, pharmaceutical, medical, and agricultural science and technology. Raman spectroscopy has intrinsic width and depth that are not associated with other spectroscopies. The width comes from the fact that it can measure a sample as it is or under any extreme conditions. First is discussed ultrafast ion association/dissociation dynamics of the sulfate ion in water and protonation/deprotonation dynamics of N,N-dimethylacetamide (DMAA) in hydrochloric acid on the basis of band-shaped analysis. Second, the discovery of the “Raman spectroscopic signature of life” and its application to monitor the life and the death of a single yeast cell are described. Then, a new nonlinear Raman method, the coherent anti-Stokes Raman scattering (CARS) signal spatial distribution measurements, to probe local structures and their temporal evolution in an ethanol/water mixture are introduced. Finally, the recent finding of the “molecular near-field effect” in which solvent vibrations intervene in the process of resonance hyper-Raman (HR) scattering, is described. This effect has a potential for selectively detecting the solvent molecules in the close vicinity of the probe b-carotene. It may lead to single-molecule spectroscopy of an ensemble of molecules.