| 概 要 |
Contemporary laser research involves use of laser spectroscopic techniques to understand the time dependent change in microscopic structural aspects, in materials or biology. In particular, Raman spectroscopy, which provides bond specific information, has attracted considerable attention.
Many advanced Raman techniques, such as, Coherent Anti-Stokes Raman scattering (CARS), picosecond (ps) Optical Kerr-gate spectroscopy and Stimulated Raman scattering(SRS), have been developed to obtain time dependent vibrational structuralinformation of various systems including fluorescent molecules with good signal to noise ratio.
Recently, we have developed a technique named “Ultra-fast Raman Loss Spectroscopy (URLS)” that has many unique advantages over the other methods. This method is analogues to FSRS, but more sensitive with better signal to noise ratio and 100% natural fluorescence rejection than SRS. Unlikein SRS, one observes URLS signals as loss (negative) signals on the blue side (higher energy) with respect to the excitation wavelength.
Thus, for an insight into the principle and origin of these intense URLS signals, the dependence of URLS signal intensity on various experiment alparameters has been carried out. URLS signal lineshape is found to be mode dependent and reflect Frank-Condon activity of the modes with in the same electronic manifold. Subsequently, the ability of URLS as a tool to acquires tructural dynamic information was demonstrated by using model systems, such as, trans stilbene and terphenyl.
References
1) B.Mallick,A.Lakshmanna, V.RadhalakshmiandS.Umapathy, CurrentScience2008;95, 1551.
2) S.Umapathy, A.Lakshmannaand B.Mallick, J.RamanSpectrosc.2009;40, 235.
3) A.Lakshmanna, B.Mallickand S.Umapathy, CurrentScience2009;97, 210.
4) S.Umapathy, B.Mallick and A.Lakshmanna, J.Chem.Phys.2010;133, 024505.
5) B.Mallick, A.Lakshmannaand S.Umapathy, J.RamanSpectrosc.2011;42, 1883.
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