Illumination Raman scattering

With regard to the confinement and enhancement ability of a metallic nano-tip, we have proposed near-field Raman microscopy using a metallic nano-tip [9]. The metallic nano-tip is able to enhance not only the illuminating light but also the Raman scattered light [9, 15, 16]. Figure 2.5 illustrates our nano-Raman microscope that mainly comprises an inverted microscope for illumination and collection of Raman... 

Occasionally, arrangements with a fibre as sensing element (Figure 7-c) are used, in particular for SERS measurements (the fibre is then coated with the SERS substrate). When using such a layout, it must be taken into account that also the Raman scattering caused by the waveguide material is recorded and must be filtered out. The same applies to arrangements where a window or any other optical element illuminated by the excitation radiation is in the field of view of the collection optics. 

In resonant Raman spectroscopy, the frequency of the incident beam is resonant with the energy difference between two real electronic levels and so the efficiency can be enhanced by a factor of 10 . However, to observe resonant Raman scattering it is necessary to prevent the possible overlap with the more efficient emission spectra. Thus, Raman experiments are usually realized under nonresonant illumination, so that the Raman spectrum cannot be masked by fluorescence. 

In such an exotic field of materials science as the amorphous (disordered) solids, one of the fundamental problems studied extensively is how to obtain insight into the stracture. Currently, it seems that versatile studies are needed to elucidate the amorphous structure. In other words, in addition to various direct and indirect structural techniques performed under fixed conditions (X-ray diffraction, Raman scattering, infrared absorption, X-ray absorption, to name a few), the investigation of structural modifications introduced by changes in composition, temperature, or pressure or induced by band-gap illumination may prove fruitful. 

A typical fibre probe will illuminate the sample with a laser spot whose dimensions are dependent on the launch optics and the position of the sample relative to the probe end. For a static sample, the volume interrogated will depend on the Raman scattering properties, working distance and the acceptance angle of the fibre collection optics. For a sample moving in the laser beam, the sampled volume is also dependent on the time taken for signal averaging and the velocity of the sample. 

When the sample is illuminated by a giant pulse of frequency v, the scattered radiation contains frequencies of 2v (hyper-Rayleigh scattering) and 2v vm (Stokes and anti-Stokes hyper-Raman scattering), where vM is a frequency of a normal vibration of the molecule. Clearly, this is Raman scattering caused by two incident photons (2v) of the laser. Experimentally, this... 

For Raman scattering measurement, a freshly cleaved sample is directly illuminated with the Ar-ion laser, and the resulting spectrum, accumulated during 10 min, is shown in Fig. 23. The band at 1580 cm 1 corresponds to the in-plane C-C breathing mode of the whole graphite lattice, namely the E2g mode. The band at 2730 cm-1 is an overtone of a lower-energy vibration, and... 

A nanosecond temperature jump is induced by an illumination of a sample with the laser heat pump. For instance, in the work of Yamamoto et al. (2000) the 1.56-pm heat pulse 9 ns width at 10 Hz was obtained through the two-step stimulating Raman scattering in D2 gas. 

In general, Stokes Raman scattering is used for spectroscopy. The intensity of the Raman scattering light is direct proportional to the number of molecules or molecule parts which are illuminated, i. e. to the concentration of molecules or molecule parts of one kind [1,2]. 

Several complementary techniques exist for the experimental study of dephasing, and here we will underline only the differences between them. The simplest experimental access to dephasing is by spontaneous Raman scattering. A laser of frequency scattered light at to, around cuj = frequency resolved. The isotropic Raman scattering cross section is directly related to the vibrational correlation function... 

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