title H, He in LTE at high densities 
c test from Ferland and Rees 88, collisions drive H to LTE
c collisions should drive all departure coef to unity
c
c commands controlling continuum =========
black body t = 50000
ionization parameter -5
c
c commands for density & abundances =========
hden = 19
init file="hheonly.ini"
set eden 20
c
c commands controlling geometry  =========
set dr -10
stop zone 1
stop lyman optical depth -6
c
c other commands for details     =========
constant temperature = 50000
iterate
c
c commands controlling output    =========
print departure coefficients h-like
print populations h-like 
print departure coefficients h-like helium
print populations h-like helium
print departure coefficients he-like
print populations he-like 
save overview "limit_lte_hhe_coll_t50.ovr"
save performance "limit_lte_hhe_coll_t50.per"
save monitors "limit_lte_hhe_coll_t50.asr" last
save dr "limit_lte_hhe_coll_t50.dr" last
c
c commands giving the monitors    =========
monitor h-like departure coef hydrogen, average 1
monitor h-like departure coef helium, average 1
c limit_lte_hhe_coll_t50.in
c class limit 
c ========================================
c 

This model is a test of the behavior of hydrogen and helium
in the high density, collision dominated, limit.
The temperature is preset, the hydrogen density is set
to a very high value, and the ionization parameter is very low.
The resulting model is collision dominated, so this case
checks that the collision physics occurs in detailed balance.
The predicted departure coefficients should all equal unity.
The set dr command sets the zone thickness to 1 cm.  

Checks:
-	Hydrogen departure coefficients exactly unity.
-	Helium departure coefficients near unity.  
	(Density not high enough to bring helium departure coefficients
	exactly to unity.)
-	H-, H2, H2+ H3+, and HeH+ departure coefficients exactly unity.
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