<p>Freeze-out is indeed a chemical term. It happens in the midplane of accretion disks where density is high enough to block UV ionization/chemical dissociation and limit heating from the central star. No one seems to have gotten around to writing up a layman friendly article on the subject yet, but these refs give the gist:</p>

<p><a href="https://books.google.com/books?id=EF1LOOgc8IcC&amp;pg=PA753&amp;lpg=PA753&amp;dq=freeze-out%20and%20UV%20dissociation%20accretion&amp;source=bl&amp;ots=YYFql7SwLC&amp;sig=xBE6cEgjLWiccc1qtIDKqSxx98U&amp;hl=en&amp;sa=X&amp;ei=LLCqVMPrC5SoyASBs4KoAw&amp;ved=0CDcQ6AEwBA#v=onepage&amp;q=freeze-out%20and%20UV%20dissociation%20accretion&amp;f=false" rel="nofollow noreferrer">Protostars and planets V</a></p>

<p><a href="http://www.stsci.edu/institute/conference/jwst2007/presentations-posters/dominik_talk.pdf" rel="nofollow noreferrer">Accretion Disks 1: During Star Formation</a></p>

<p><a href="https://books.google.com/books?id=EWURgHzF3DQC&amp;pg=PA11&amp;lpg=PA11&amp;dq=freeze-out%20and%20UV%20dissociation&amp;source=bl&amp;ots=B5EMwewH6m&amp;sig=IqQjpyuoQYFTYQ_Ih8cFmugShUo&amp;hl=en&amp;sa=X&amp;ei=Ya-qVIHLOYKZyAST7YKoAw&amp;ved=0CDQQ6AEwBA#v=onepage&amp;q=freeze-out%20and%20UV%20dissociation&amp;f=false" rel="nofollow noreferrer">Organic Matter in Space (IAU S251) Evolution of Organic Matter</a></p>

<p>From ref 2:</p>

<p><img src="https://i.sstatic.net/41zQX.png" alt="enter image description here"></p>

CC BY-SA 3.0
2015-01-05T19:13:22.577Z
Aah, so ist pretty much the same thing as the dead zone? I am not sure if they are related, but I actually am using the Protostars and planets IV conference on YouTube for my research, so maybe there are different speakers that are just using different terminology for the same phenomena. Thank you, I will certainly read your links!
L.R.
CC BY-SA 3.0
2015-01-05T15:59:24.203Z
2015-01-05T15:59:24.203Z
Wayfaring Stranger
<p>I was recently watching a video on the physics and chemistry in planetary accretion disks, and the speaker at a certain point mentioned 'freeze-out and UV dissociation'. Is freeze-out a purely chemical term, or is it specific for this process? Is it very important in planetary formation? </p>

<accretion-discs>
Astrochemistry - what does freeze-out mean?
L.R.
# Astrochemistry - what does freeze-out mean?

(Asked by: username_0 on 2015-01-04)

I was recently watching a video on the physics and chemistry in planetary accretion disks, and the speaker at a certain point mentioned 'freeze-out and UV dissociation'. Is freeze-out a purely chemical term, or is it specific for this process? Is it very important in planetary formation?

**Tags:** accretion-discs

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## 1 answers

### Answer by username_1 on 2015-01-05. Score: 3 | Accepted answer

Freeze-out is indeed a chemical term. It happens in the midplane of accretion disks where density is high enough to block UV ionization/chemical dissociation and limit heating from the central star. No one seems to have gotten around to writing up a layman friendly article on the subject yet, but these refs give the gist:

[Protostars and planets V](https://books.google.com/books?id=EF1LOOgc8IcC&pg=PA753&lpg=PA753&dq=freeze-out%20and%20UV%20dissociation%20accretion&source=bl&ots=YYFql7SwLC&sig=xBE6cEgjLWiccc1qtIDKqSxx98U&hl=en&sa=X&ei=LLCqVMPrC5SoyASBs4KoAw&ved=0CDcQ6AEwBA#v=onepage&q=freeze-out%20and%20UV%20dissociation%20accretion&f=false)

[Accretion Disks 1: During Star Formation](http://www.stsci.edu/institute/conference/jwst2007/presentations-posters/dominik_talk.pdf)

[Organic Matter in Space (IAU S251) Evolution of Organic Matter](https://books.google.com/books?id=EWURgHzF3DQC&pg=PA11&lpg=PA11&dq=freeze-out%20and%20UV%20dissociation&source=bl&ots=B5EMwewH6m&sig=IqQjpyuoQYFTYQ_Ih8cFmugShUo&hl=en&sa=X&ei=Ya-qVIHLOYKZyAST7YKoAw&ved=0CDQQ6AEwBA#v=onepage&q=freeze-out%20and%20UV%20dissociation&f=false)

From ref 2:

![enter image description here](https://i.sstatic.net/41zQX.png)

> **Comments:**
> **username_0**: Aah, so ist pretty much the same thing as the dead zone? I am not sure if they are related, but I actually am using the Protostars and planets IV conference on YouTube for my research, so maybe there are different speakers that are just using different terminology for the same phenomena. Thank you, I will certainly read your links!  

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