<p>The natural linewidth also causes absorption lines to be broadened in exactly the same way.</p>
<p>Usually, the natural linewidth is <em>far</em> narrower than the width caused by (i) Doppler broadening by thermal motions of the atoms/molecules, (ii) collisional broadening caused by interactions between atoms/molecules, (iii) the broadening imposed by the finite spectral resolution of the instrument being used to measure the spectrum.</p>

CC BY-SA 4.0
2022-11-15T21:43:12.747Z
Collisional broadening does not lead to a Gaussian profile but also a Lorentzian profile (effectively, it reduces the natural lifetime of the state). So it would not be distinguishable from natural broadening as such. See e.g.  http://www-star.st-and.ac.uk/~kw25/teaching/nebulae/lecture08_linewidths.pdf for more details
Thomas
CC BY-SA 4.0
2022-11-16T09:37:33.020Z
@Thomas agreed.
ProfRob
CC BY-SA 4.0
2022-11-15T11:32:00.853Z
2022-11-16T07:29:19.130Z
2022-11-16T07:29:19.130Z
ProfRob
<p>Emission lines have a certain natural width. Due to the uncertainty principle systems that spontaneously decay or produce radiation have a fundamental energy blur, and their radiation has a corresponding natural line width.</p>
<p>I am wondering how that phenomenon translates to absorption lines?</p>

<observational-astronomy><spectroscopy><spectra><electromagnetic-spectrum>
Natural line width from absorption lines
trynerror
# Natural line width from absorption lines

(Asked by: username_0 on 2022-11-15)

Emission lines have a certain natural width. Due to the uncertainty principle systems that spontaneously decay or produce radiation have a fundamental energy blur, and their radiation has a corresponding natural line width.

I am wondering how that phenomenon translates to absorption lines?

**Tags:** observational-astronomy, spectroscopy, spectra, electromagnetic-spectrum


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## 1 answers

### Answer by username_1 on 2022-11-15. Score: 9 | Accepted answer

The natural linewidth also causes absorption lines to be broadened in exactly the same way.

Usually, the natural linewidth is *far* narrower than the width caused by (i) Doppler broadening by thermal motions of the atoms/molecules, (ii) collisional broadening caused by interactions between atoms/molecules, (iii) the broadening imposed by the finite spectral resolution of the instrument being used to measure the spectrum.

> **Comments:**
> **username_2**: Collisional broadening does not lead to a Gaussian profile but also a Lorentzian profile (effectively, it reduces the natural lifetime of the state). So it would not be distinguishable from natural broadening as such. See e.g.  http://www-star.st-and.ac.uk/~kw25/teaching/nebulae/lecture08_linewidths.pdf for more details  
> **username_1**: @username_2 agreed.  

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