WOLFRAM|DEMONSTRATIONS PROJECT

Helium Ionization Fraction as Function of Density and Temperature

​
log
10
ρ
-4
y
1
y
2
y
0
y
e
The ionization fraction of helium is determined by the temperature and density of the plasma. At a particular density
ρ
and temperature
T
, some fraction of helium will be neutral
(
y
0
)
, some fraction will be singly ionized
(
y
1
)
, and some fraction will be doubly ionized
(
y
2
)
. At the same time, the number of electrons per helium nucleus
(
y
e
)
is determined by charge neutrality. You can set
log
10
ρ
with
ρ
in cgs units (
g
-3
cm

to see the ionization fraction as temperature
T
varies from 40,000 K to 200,000 K.