• S Umapathy

      Articles written in Journal of Chemical Sciences

    • Laser Raman spectroscopy of colloidal semiconductor photosensitizers

      S Umapathy R E Hester

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      Colloidal semiconductor photosensitizers have been used as heterogeneous catalysts for the chemical solar energy conversion processes. The use of Raman spectroscopy to address the problems related to colloidal semiconductors and photosensitization reactions is reviewed. In particular, the adsorption characteristics of various secondary sensitizers and their electron-transfer reactions are studied using resonance Raman and time-resolved resonance Raman spectroscopy. Finally, the importance of the quantum size effect of colloidal semiconductors in relation to their catalytic effects is presented with particular reference to their influence on photosensitizing properties.

    • Resonance Raman spectroscopic investigation of MLCT character in Schiff base ferrocenyl complexes

      B Abraham B Karthikeyan Sushanta K Pal A G Samuelson S Umapathy

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    • Basic principles of ultrafast Raman loss spectroscopy

      N K Rai A Y Lakshmanna V V Namboodiri S Umapathy

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      When a light beam passes through any medium, the effects of interaction of light with the material depend on the field intensity. At low light intensities the response of materials remain linear to the amplitude of the applied electromagnetic field. But for sufficiently high intensities, the optical properties of materials are no longer linear to the amplitude of applied electromagnetic field. In such cases, the interaction of light waves with matter can result in the generation of new frequencies due to nonlinear processes such as higher harmonic generation and mixing of incident fields. One such nonlinear process, namely, the third order nonlinear spectroscopy has become a popular tool to study molecular structure. Thus, the spectroscopy based on the third order optical nonlinearity called stimulated Raman spectroscopy (SRS) is a tool to extract the structural and dynamical information about a molecular system. Ultrafast Raman loss spectroscopy (URLS) is analogous to SRS but is more sensitive than SRS. In this paper, we present the theoretical basis of SRS (URLS) techniques which have been developed in our laboratory.

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