Raman temporal method

For some systems, there is no resonance Raman or SERS effect to be utilized, and the sensitivity becomes the main problem. In this case, a potential difference method will be of great help [11], Here, a spectrum is acquired at potentials where there is no or only a weak surface signal which is subtracted from that at the potential of interest. In addition, a change in the composition of the electrolyte or an isotopic labeling experiment may be considered to identify the surface species and verify its orientation and structure. For temporally resolved studies, electrochemical transient techniques are helpful to understand the surface dynamics and the reconstruction processes of surfaces. For nonuniform surfaces, spatially resolved measurements provide more reliable and complete information on the surface. This is also useful for electrode surfaces that change either chemically or topographically in a microzone upon variation of potential. 

It follows from Eqs. (26) and (29) that, once F is determined, by the method described in the earlier sections of this paper, a further analysis of the full I(At) becomes possible in terms of the integration over the temporal profiles of the laser fields E (t), plus an independent evaluation of the Raman tensor elements R. ... 

Recently, the femtosecond time-resolved spectroscopy has been developed and many interesting publications can now be found in the literature. On the other hand, reports on time-resolved vibrational spectroscopy on semiconductor nanostructures, especially on quantum wires and quantum dots, are rather rare until now. This is mainly caused by the poor signal-to-noise ratio in these systems as well as by the fast decay rates of the optical phonons, which afford very fast and sensitive detection systems. Because of these difficulties, the direct detection of the temporal evolution of Raman signals by Raman spectroscopy or CARS (coherent anti-Stokes Raman scattering) [266,268,271-273] is often not used, but indirect methods, in which the vibrational dynamics can be observed as a decaying modulation of the differential transmission in pump/probe experiments or of the transient four-wave mixing (TFWM) signal are used. 

In cooperation with the project (Brauer et al.. University of Erlangen- Chap. 24), recent studies [28] demonstrate a strategy to quantify the evaporatimi rate as a function of the droplet composition by combining shadowgraphy and Raman spectroscopy. They showed the possibility to determine the composition of levitated acetone/water droplets with a temporal and spatial resolution so that they could obtain informatimi about the radial distribution of separate components inside the droplet. As a next step, it would be interesting to get access to composition profiles of solutes like polymers inside a droplet. With the help of this method, it could be possible to track the evolution of the polymer concentration so that further information about the mass transport and shell formation can be obtained. 

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