Rayleigh band

Physically, the Brillouin spectrum arises from the inelastic interaction between a photon and the hydrodynamics modes of the fluid. The doublets can be regarded as the Stokes and anti-Stokes translational Raman spectrum of the liquid. These lines arise due to the inelastic collision between the photon and the fluid, in which the photon gains or loses energy to the phonons (the propagating sound modes in the fluid) and thus suffer a frequency shift. The width of the band gives the lifetime ( 2r)-1 of a classical phonon of wavenumber q. The Rayleigh band, on the other hand, represents the... 

Fig. 8.12 The Raman effect. Monochromatic light of frequency vQ is scattered by a sample, either without losing energy (Rayleigh band) or inelastically, in which a vibration is excited (Stokes band), or a vibra-tionally excited mode in the sample is de-excited (anti-Stokes band). The spectrum is that of the light scattered by the sample. The energy level diagrams illustrate that the scattering process occurs via highly unstable states of high energy.

A. De Santis and M. Sampoli. Depolarized Rayleigh bands of fluid CO at room temperature Induced effects on the second moment. Phys. Lett. A, 700 25-27 (1984). 

H. Versmold and U. Zimmermann. Density dependence of interaction-induced scattering Contributions to the depolarized Rayleigh band of ethane. J. Chem. Soc. Faraday Trans. 2, 53 1815-1824 (1987). 

Figure 2. Experimental depolarization ratio r](,p(v) — /(/ v) /// (v) of the binary Rayleigh band of gaseous CF4 ( + ) at 294.5 K. The depolarization ratio for the V Raman band is also...

Usually y < 1. Then the spectrum consists of a very narrow central band due entirely to the translational motion (this is called the Rayleigh band), and a broad symmetrical doublet shifted from the central line due entirely.to the rotations. 

Where y was defined previously. Usually y > 1. Thus the spectrum consists of a narrow central band resulting from the first term on the right-hand side of Eqs. (7.6.5), due entirely to translational motion17 (the Rayleigh band) and a broad symmetrical doublet arising from the second term on the right-hand side of Eqs. (7.6.4c) due entirely to the rotational motion. This spectrum is shown schematically in Fig. 7.6.1. 

This is a matter of some urgency for us since in most biological applications it is assumed that the central (or Rayleigh) band is dependent on the diffusion coefficient and nothing else. This assumption enables the biochemist to determine diffusion coefficients (cf. Section 5.4). Let us explore this assumption further. 

Figure 4.4. The Stokes and anti-Stokes Raman spectrum of sulphur at 1064 nm laser excitation. The feature between 9300 and 9394 cm is an experimental artefact due to the optical filter used to suppress the very intense Rayleigh band.

NIR-FT-Raman spectra of skin from pig ear, guinea pig and mouse were recorded with excitation at 1064 nm and compared to spectra of human skin. The R(V )-representation was used to eliminate the intense Rayleigh band. The total water content in each sample was estimated from the intensities of the OH-stretching vibrations at about 3200 cm. A low-wavenumber band around 180 cm (- 5.5 terahertz) was characteristic of a bulk-like liquid water structure. Water content and structure in skin from pig ear, guinea pig and human were similar and different from mouse skin. Differences in loss of bulk water were observed for skin samples after freezing and thawing. Skin biopsies of human skin with various skin tumors showed an increase of water with a bulk-like structure in skin with malignant skin tumors. 

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