November 12, 2019, 12:11:09 PM
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Topic: Understanding rot-vibrational and electronic spectra  (Read 706 times)

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Offline paulhao

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Understanding rot-vibrational and electronic spectra
« on: March 02, 2019, 06:05:11 PM »
I have a hard time understanding the difference between rotational spectrum, vibrational spectrum, rot-vibrational spectrum and electronic spectrum. I have read some books and explanation but still feel so confused about the basic difference among those spectra.

Can anyone explain this to me please, Thanks

Offline Borek

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Re: Understanding rot-vibrational and electronic spectra
« Reply #1 on: March 03, 2019, 03:29:25 AM »
If you have read about them can you define each?
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Offline Corribus

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Re: Understanding rot-vibrational and electronic spectra
« Reply #2 on: March 03, 2019, 12:02:55 PM »
We will need you to be more specific about where you're having trouble. As stated, the question is really too broad.
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Offline paulhao

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Re: Understanding rot-vibrational and electronic spectra
« Reply #3 on: March 03, 2019, 04:20:09 PM »
We will need you to be more specific about where you're having trouble. As stated, the question is really too broad.

If you have read about them can you define each?

Well, as I understand,

 Rotational spectra occur by rotation of molecule in microwaves region


Vibrational spectra occur by vibration of molecule around its principal axis in infrared waves.


Electronic spectra happen when an electron jumps from one electronic level to another in ultraviolet radiations


Is my understanding right or is it missing some fundamental concepts?

Offline mjc123

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Re: Understanding rot-vibrational and electronic spectra
« Reply #4 on: March 04, 2019, 08:37:45 AM »
That's basically right (except that molecules don't vibrate "around the principal axis"). It is complicated by the fact that vibrational transitions may be accompanied by a change in the rotational state, and electronic transitions may be accompanied by a change in both the vibrational and rotational states ("rovibronic" transitions).
The appearance and interpretation of each kind of spectrum is different, as the energy level structure and selection rules differ for each kind. Thus, for example, I have done a lot of vibrational spectroscopy, much less electronic, and very little rotational; so I would be much more comfortable interpreting a vibrational spectrum than the other kinds.

You still haven't told us what it is you don't understand. Have you got any specific questions?

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