### ionization fraction

**(electron fraction)**
(a substance's ratio of unattached electrons to nuclei)

**Electron fraction** and **ionized fraction**
are generally the ratio of unattached electrons to nuclei.
The former is the ratio of unattached electrons to nuclei and
molecules, and the latter, the ratio of ions to all nuclei and
molecules. The two are sometimes used interchangeably and in the
simple/common case of monatomic hydrogen and positive ions,
the two would be the same and knowing one is knowing the other,
and in this case, the number is also the number of unattached
protons.
I've seen them symbolized by **Y**_{e} or **x**_{e}.

(*ionization,hydrogen,plasma*)
**Further reading:**

http://scienceworld.wolfram.com/physics/IonizationFraction.html

http://www.astro.sunysb.edu/dswesty/explode.html

**Referenced by pages:**

r-process

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