Level Population Ratios

This webpage contains all the necessary information to determine the electron number density from level population ratios of various ions at certain temperatures.
For the elements listed below, each clickable ion will direct to plots and tables containing information on specific line transitions and population ratios.
1) The line transition tables contain wavelengths, oscillator strengths, Gaunt factors, energy levels and ion numbers.
2) The population ratio tables have the population ratios between an excited energy level and the ground energy level for a given ion. All population ratios were calculated using the CHIANTI 8.0.7 database. CHIANTI is a collaborative project involving George Mason University, the University of Michigan (USA), and the University of Cambridge (UK).
3) The population ratio plots show the ratio as a function of electron number density for specific temperatures. Each ion will have four different plots for a given ratio. In each plot, we show population ratios as a function of electron number density for five temperatures. The first and second plots are the population ratios in linear and log values, respectively, for the first group of temperatures. The third and fourth plots are the population ratios in linear and log values, respectively, for the second group of temperatures.

Click on the appropriate ion to access plots, line lists and population ratio tables.
Here is an example plot.
Here is an example table.

He I

C II III

N II III IV

O I II III IV V

Ne II III IV V VI VII

Na IV V VI VII VIII

Mg II V VI VII VIII IX

Al II VII VIII IX

Si II III IV VIII IX X

S II III IV V XI

Cl II IV

Ar III V

K V VI

Ca II V VII VIII

Fe II III V

Ni II

Supplemental tables

atom1
atom2
Completed H table

He	I
C		II	III
N		II	III	IV
O	I	II	III	IV	V
Ne		II	III	IV	V	VI	VII
Na				IV	V	VI	VII	VIII
Mg		II			V	VI	VII	VIII	IX
Al		II					VII	VIII	IX
Si		II	III	IV				VIII	IX	X
S		II	III	IV	V						XI
Cl		II		IV
Ar			III		V
K					V	VI
Ca		II			V		VII	VIII
Fe		II	III		V
Ni		II