Rotational and vibrational spectroscopy

In summary, the spacing between rotational energy levels increases as J does in microwave spectroscopy. For IR, the selection rule is Δv=±1 when using IR light, but it can also be Δv=±0,1 when using UV light in electronic transitions. This is because the equilibrium positions of the electronic ground and excited state do not coincide, resulting in a series of transitions with different v values.
  • #1
Chemist20
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Hello there!

Im studying microwave spectroscopy, and I'm stuck because I don't see why the spacing between rotational energy levels increases as J does. Can anyone explain please?

Also, about IR, I see everywhere that the selction rule is Δv=±1. Correct me if I'm wrong but I'm guessing that's only when you use IR light. If you where to use UV, where an electronic transition can take place, we could also go from l=1 v=0 to l=2 v=0 and hence Δv=±0,1. (excluding overtones of this) . Is this correct?

Thanks!
 
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  • #2
In electronic transitions you usually observe a whole series of transitions of possible v values (so called Franck Condon progression) as the equilibrium positions of the electronic ground and excited state do not coincide.
 

What is rotational and vibrational spectroscopy?

Rotational and vibrational spectroscopy is a branch of spectroscopy that studies the energy levels and transitions of molecules due to their rotational and vibrational motion.

How does rotational and vibrational spectroscopy work?

Rotational and vibrational spectroscopy works by using electromagnetic radiation, such as infrared light, to excite the rotational and vibrational energy levels of molecules. As the molecules absorb the energy, they undergo changes in their rotational and vibrational motion, which can be detected and measured by a spectrometer.

What types of information can be obtained from rotational and vibrational spectroscopy?

Rotational and vibrational spectroscopy can provide information about the structure, composition, and dynamics of molecules. It can also be used to identify and quantify the chemical bonds present in a molecule, as well as determine the symmetry and orientation of molecules.

What are the applications of rotational and vibrational spectroscopy?

Rotational and vibrational spectroscopy has various applications in fields such as chemistry, biology, physics, and medicine. It is commonly used in the analysis of organic and inorganic compounds, as well as in the study of molecular interactions and reactions. It also has applications in environmental monitoring, food safety, and pharmaceutical development.

What are the advantages of rotational and vibrational spectroscopy?

Rotational and vibrational spectroscopy is a non-destructive and non-invasive technique that can provide highly specific and quantitative information about molecules. It is also relatively fast and requires minimal sample preparation. Additionally, it can be used to analyze samples in various physical states, such as gases, liquids, and solids.

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