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  Rotational Raman Spectroscopy
Intensities of Spectral Lines page 1 of 2
   
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Introduction
The Raman Effect
Experimental Techniques
1. Rotational Raman Spectroscopy
Interpreting the Spectrum
Effect of Bond Length
Centrifugal Distortion
Intensities of Spectral Lines
Nuclear Spin Statistics
2. Real Diatomic Molecules
Temperature
Spectrum of Nitrogen
Isotopic Substitution
Nuclear Spin Statistics
Predict the Spectrum of Oxygen
  Spectra lines have a position and a height. The position of lines has been described as the separation of energy levels. The next section will attempt to give meaning to the intensity of spectral lines.

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The intensity of spectral lines is determined by the relative probabilities transitions between various energy levels. Selection rules for rotational Raman allow only J=2.

Q4.1 The intrinsic probability for a transition of a single molecule from J = 0 to J = 2 is the same as that for a transition from J = 1 to J = 3. Why are not all spectral lines equally intense?
Q4.2 What is the relationship between the intensities of the Stokes and Anti-Stokes lines? Explain this in terms of the population of the energy levels.


The reason that the intensity of the spectral lines tail to zero is the influence on populations of an exponential term:
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