4.1. Testcase #1
In this example we calculate the population ratios of the 3PJ ground levels of atomic carbon as a function of neutral hydrogen density. These population ratios are a useful density estimator [19] and are needed to interpret ratios of UV C I fine structure absorption lines observed in damped Lyman- QSO absorbers [20, 21, 22], for example.
We take into account collisions with several collisional partners - electron, proton, neutral hydrogen, para/ortho molecular hydrogen, neutral helium -, tying their densities to the neutral hydrogen density nH0 according to:
We also take into account the effect of CMBR at a redshift z = 1
and the radiation field of the Galaxy.
In the high density limit, function LTEDEV is called to show that the
population ratios differ
from LTE conditions by less than 4% .
To run this testcase the user should include the radiation field of the
Galaxy in the body
of function URAD in module POPRATIO:
urad = Fgal(lambda)