information on raman effect formula???
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Answer:
Explanation:The energy difference between the incident and scattered photons is represented by the arrows of different lengths in Figure 1. Numerically, the energy difference between the initial and final vibrational levels, , or Raman shift in wave numbers (cm-1), is calculated through equation 1 in which l incident and l scattered are the wavelengths (in cm) of the incident and Raman scattered photons, respectively.
The vibrational energy is ultimately dissipated as heat. Because of the low intensity of Raman scattering, the heat dissipation does not cause a measurable temperature rise in a material.
At room temperature the thermal population of vibrational excited states is low, although not zero. Therefore, the initial state is the ground state, and the scattered photon will have lower energy (longer wavelength) than the exciting photon. This Stokes shifted scatter is what is usually observed in Raman spectroscopy. Figure 1. depicts Raman Stokes scattering.
A small fraction of the molecules are in vibrationally excited states. Raman scattering from vibrationally excited molecules leaves the molecule in the ground state. The scattered photon appears at higher energy, as shown in Figure 2. At room temperature the anti-Stokes-shifted Raman spectrum is always weaker than the Stokes-shifted spectrum and since the Stokes and anti-Stokes spectra contain the same frequency information most Raman experiments look at Stokes-shifted scatter only.
