Raman scattering experimental design

Measurement of the total Raman cross-section is an experimental challenge. More connnon are reports of the differential Raman cross-section, doj /dQ, which is proportional to the intensity of the scattered radiation that falls within the element of solid angle dQ when viewing along a direction that is to be specified [H]. Its value depends on the design of the Raman scattering experiment. 

The experimental setup employed 785 nm excitation with a 90° collection geometry. Each spectrum was obtained with excitation power 300 mW and integration time equivalent to 2.5 min. Because filtered serum is nearly transparent at 785 nm, excitation of Raman scattering is effectively along the entire laser path, creating a line source in the cuvette. Thus, the authors surmise that better collection efficiency could be obtained with optics designed specifically for this type of source, as opposed to the standard spherical lens they employed. 

In all these time-resolved experiments the principles of pump-probe laser spectroscopy are the key element in the experimental design. A laser pulse is optically split into two components of unequal amplitude. The intense fraction, acting as a pump piilse, is directed towards the target or sample cell to trigger the molecular event under study. The much attenuated probe pulse monitors the absorption, raman scattering, polarization, coherence, or phase shift, which is linked explicitly to the dynamical observable under investigation. Extremely precise time... 

The surface-enhanced fluorescence, SEF, and surface-enhanced Raman scattering, SERS, phenomena are inextricably tied to one another due to their conunon electromagnetic enhancement origin, and thus there is a very strong overlap in their lit ature. In fact, there is often a direct competition between fluorescence and Raman scattering that, as we shall see, with strategic experimental design, can be exploited. There are, however, a few very important points on which these two effects differ, the most important of which is their distance dependence. 

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