Rotational Spectra: Why Absorption & Not Emission Lines?

In summary, the pure rotational spectrum is typically observed as absorption lines rather than emission lines due to the ease of handling and the ability to derive more information from the absorption lines. However, there have been some instances, such as with far-infrared lasers, where emission lines of rotational spectra have been observed.
  • #1
koustav
29
4
why pure rotational spectrum is almost always seen as absorption lines,and not as emission lines?
 
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  • #2
koustav said:
why pure rotational spectrum is almost always seen as absorption lines,and not as emission lines?
there exists both spectra absorption and emission but

people focus on absorption as its easier to handle and more info can

be derived...the intensities are good ...see for details

Reference:< http://www.pci.tu-bs.de/aggericke/PC4e_osv/Spectroscopy050119/node18.html>
 
  • #3
koustav said:
why pure rotational spectrum is almost always seen as absorption lines,and not as emission lines
That's probably because people are most likely to look into the absorption lines.
However, at one point I was playing with a far-infrared laser. I didn't make much progress but I believe, these were emission lines of rotational spectra
 

1. What is rotational spectroscopy?

Rotational spectroscopy is a branch of spectroscopy that studies the absorption or emission of electromagnetic radiation by molecules due to their rotational energy levels.

2. Why do rotational spectra show absorption lines rather than emission lines?

This is because rotational transitions in molecules typically involve a change in the rotational energy levels from a lower to a higher state, which results in the absorption of radiation rather than emission.

3. How is rotational spectroscopy used in scientific research?

Rotational spectroscopy is used to identify and study the structure and composition of molecules in various fields such as chemistry, physics, and astronomy. It can also be used to measure physical properties of molecules, such as bond lengths and dipole moments.

4. What types of molecules can be studied using rotational spectroscopy?

Rotational spectroscopy can be used to study any molecule that has a permanent electric dipole moment, which includes most molecules composed of two or more atoms. It is particularly useful for studying small and simple molecules.

5. How does rotational spectroscopy differ from other types of spectroscopy?

Unlike other types of spectroscopy, such as infrared or ultraviolet spectroscopy, rotational spectroscopy specifically focuses on the rotational energy levels of molecules. It is also a highly accurate and precise method for measuring molecular properties, making it particularly useful in analytical chemistry.

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