<p>As your question is based on the plot you posted, I suggest you to look for a lower wavelength range of the atmospheric electromagnetic absorption. A quick search in google gave me <a href="https://www.nat.vu.nl/en/Images/Vieitez-08-ML_tcm208-84511.pdf" rel="noreferrer">this paper</a>, which says:</p>
<blockquote>
<p>The importance of molecular nitrogen as the most abundant species in the Earth's atmosphere is evident. The strong absorption bands in the range 80–100 nm shield the Earth's surface from theextreme ultraviolet (XUV) part of the solar radiation.</p>
</blockquote>
<p>As you can see, the absorption bands of diatomic nitrogen resides in the &lt;1000 nm, which is in the extreme left of your plot, shadowed by its scale (1 micrometer = 1000 nanometers).</p>

CC BY-SA 4.0
2020-06-30T22:22:27.413Z
2020-06-30T22:22:27.413Z
SebaGM
<p>The transmission spectrum of the Earth atmosphere is like that (<a href="https://www.cfa.harvard.edu/%7Elkaltenegger/KalteneggerTraubApJ09.pdf" rel="noreferrer">Kaltenegger &amp; Traub 2009</a>):</p>
<p><a href="https://i.sstatic.net/EWWZf.png" rel="noreferrer"><img src="https://i.sstatic.net/EWWZf.png" alt="enter image description here" /></a></p>
<p>As you can see, you can find many absorption lines related to some components of Earth's atmosphere: H<span class="math-container">$_2$</span>O, O<span class="math-container">$_2$</span>, CO<span class="math-container">$_2$</span>, O<span class="math-container">$_3$</span>, CH<span class="math-container">$_4$</span>... But the nitrogen, N<span class="math-container">$_2$</span>, is not detected anywhere in the spectrum. Why N<span class="math-container">$_2$</span> is not detected, but O<span class="math-container">$_2$</span>, for example, is?</p>

CC BY-SA 4.0
2020-06-30T22:35:28.340Z
This might be usefully asked on Chemistry stack.
James K
CC BY-SA 4.0
2020-06-30T23:36:33.620Z
conversely, Chemistry SE can be [invited here](https://chat.stackexchange.com/transcript/message/54812463#54812463), as can [Earth Science SE](https://chat.stackexchange.com/transcript/message/54812485#54812485)
uhoh
CC BY-SA 4.0
2020-07-01T12:55:27.843Z
As the answer points out, the first thing to do is to look up the absorption wavelengths (or spectral map) for N2 .
Carl Witthoft
<spectroscopy><astrobiology>
Why N$_2$ is a non-absorbing species in the spectrum of the Earth?
Carlos Vázquez Monzón
# Why N$_2$ is a non-absorbing species in the spectrum of the Earth?

(Asked by: username_0 on 2020-06-30)

The transmission spectrum of the Earth atmosphere is like that ([Kaltenegger & Traub 2009](https://www.cfa.harvard.edu/%7Elkaltenegger/KalteneggerTraubApJ09.pdf)):

[![enter image description here](https://i.sstatic.net/EWWZf.png)](https://i.sstatic.net/EWWZf.png)

As you can see, you can find many absorption lines related to some components of Earth's atmosphere: H$\_2$O, O$\_2$, CO$\_2$, O$\_3$, CH$\_4$... But the nitrogen, N$\_2$, is not detected anywhere in the spectrum. Why N$\_2$ is not detected, but O$\_2$, for example, is?

**Tags:** spectroscopy, astrobiology
> **Comments:**
> **username_1**: This might be usefully asked on Chemistry stack.  
> **username_2**: conversely, Chemistry SE can be [invited here](https://chat.stackexchange.com/transcript/message/54812463#54812463), as can [Earth Science SE](https://chat.stackexchange.com/transcript/message/54812485#54812485)  
> **username_3**: As the answer points out, the first thing to do is to look up the absorption wavelengths (or spectral map) for N2 .  

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## 1 answers

### Answer by username_4 on 2020-06-30. Score: 8

As your question is based on the plot you posted, I suggest you to look for a lower wavelength range of the atmospheric electromagnetic absorption. A quick search in google gave me [this paper](https://www.nat.vu.nl/en/Images/Vieitez-08-ML_tcm208-84511.pdf), which says:

> The importance of molecular nitrogen as the most abundant species in the Earth's atmosphere is evident. The strong absorption bands in the range 80–100 nm shield the Earth's surface from theextreme ultraviolet (XUV) part of the solar radiation.

As you can see, the absorption bands of diatomic nitrogen resides in the <1000 nm, which is in the extreme left of your plot, shadowed by its scale (1 micrometer = 1000 nanometers).


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