21-Spectro_5_web - Definitions (spectroscopy) there is only...

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Definitions (spectroscopy) “there is only one physics” (general analysis of nature)
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Raman spectroscopy Lasers
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Polarization   refers to the through-bond or through-space (inductive) influence of an electronic properties of a substituent on a distribution of an electronic charge of a molecule. This concept is based on formation of an electric dipole within a molecule, which is generally not related to the polarization of electromagnetic waves. Polarization  – typically - is a property of light that describes the orientation  of oscillations. Light exhibit polarization; acoustic waves in a gas or liquid do  not. The  polarization  of an electromagnetic (EM) wave is a complex PC issue. Electric polarizability is the relative tendency of a charge distribution of an atom or a molecule to be distorted from its normal shape by an external electric field , which may be caused by the presence of a nearby ion, by dipole or by LIGTH . The electronic polarizability α is defined as the ratio of the induced dipole moment of an atom to the electric field that produces this dipole moment.  
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RAMAN SPECTROSCOPY   Raman spectroscopy involves light  scattering  that results from  interactions between photons and vibrational energy levels. Elastic scattering ,  frequency of scattered radiation,  ν (observed)  is equal  to  the frequency of incident radiation,  ν (incident source):  ν  (observed) =  ν  (incident source) Inelastic scattering ,  the scattered radiation energy  is not equal  to the incident  radiation energy, usually is smaller: ν  (observed) <  ν  (incident source) In Raman spectroscopy,  inelastic  light scattering is quite weak and spectra  may be difficult to analyze, the application of  lasers   as excitation sources is  essential.
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Inelastic scattering ν  (observed) <  ν  (incident source),  a  fraction of energy  is imparted  in the system that causes light  scattering: THE STOKES LINES In some unusual instances energy is transferred from the  illuminated object to the scattered radiation.  If this is so: ν  (observed) >  ν  (incident source) THE ANTI-STOKES LINES
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Rayleigh scattering (elastic): the secondary waves of the same frequency than the source (that result from vibrating electrons) are propagated in all directions Inelastic scattering (different frequency) is the source of analytical information in Raman spectroscopy
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Elastic Rayleigh Scattering (elastic) 1. Electric field of electromagnetic radiation interacts with electrons of the sample causing periodic polarization
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21-Spectro_5_web - Definitions (spectroscopy) there is only...

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