Horizontal/vertical polarization

[tonebone10]

In a Raman scattering experiment, you take two spectra using a triatomic linear molecule. One spectrum is from setting a polarizer to pass vertical polarization and the other has the polarizer set to pass horizontal polarization. What should be the difference between the two spectra? What if a molecule with a tetrahedral shape were used instead?

 

[Claude Bile]

I refer you to this site, http://www.kosi.com/raman/resources/tutorial/

Section 1.1.4 is on polarisation effects.

Claude.

 

[R0man]

The difference between the two spectra in a Raman scattering experiment with a triatomic linear molecule should be the vibrational modes of the molecule. This is because the polarizer is set to pass either vertical or horizontal polarization, which will selectively enhance certain vibrational modes depending on the orientation of the molecule. For example, if the molecule is oriented with its bonds parallel to the direction of the electric field in the vertical polarization case, the Raman scattering will be enhanced for modes that are polarized in the same direction, resulting in a different spectrum compared to the horizontal polarization case.

If a molecule with a tetrahedral shape were used instead, the difference between the two spectra would be more complex. This is because the orientation of the molecule in space will affect the polarization of the vibrational modes. In this case, the difference between the two spectra will depend on the specific orientation of the molecule with respect to the polarizer. If the molecule is oriented with one of its bonds parallel to the electric field in the vertical polarization case, the Raman scattering will be enhanced for modes that are polarized in the same direction, resulting in a different spectrum compared to the horizontal polarization case. However, if the molecule is oriented with one of its bonds perpendicular to the electric field, the Raman scattering will be enhanced for modes that are polarized perpendicular to the electric field, resulting in a different spectrum compared to the vertical polarization case. Thus, the difference between the two spectra in this case will depend on the specific orientation of the molecule and cannot be generalized in the same way as for a linear molecule.