title case A
c 
c Seaton, M.J, 1959 MN 119, 90, 
c 4pi j(beta) 5.56E-26
c for this model total H-beta=4.745
c b(2)=3.73E-3 (3)=3.69E-2 (4)=0.091 (5)=0.145 (6)=0.193
c n.b. very different results if not l-mixed
c
c commands controlling continuum =========
black body, T = 50000 K
ionization parameter -2
c
c commands for density & abundances =========
hden = 13;
init file="honly.ini"
c
c commands controlling geometry  =========
stop lyman optical depth -6
stop zone 1
set dr 0
c
c other commands for details     =========
no induced processes (OK) ;N.B. case A is a fiction; no incuded transitions
atom h-like collisions off ; must turn off all collisions 
constant temperature = 10000 K
iterate
c
c commands controlling output    =========
c this should make the predicted totl Hbeta near unity for case a
normalize to "CaBo" 4861 = 2.23
print populations h-like 
print departure coefficients
save overview "limit_casea_h_den13.ovr"
save performance "limit_casea_h_den13.per"
save monitors "limit_casea_h_den13.asr" last
c
c commands giving the monitors    =========
//
// >>chng 07 oct 22, from 1.91 to 3.29, resolve l-levels of h-like sequence 
// >>chng 08 apr 10, from 3.29 to 3.60, change default h-like levels, other minor changes
// >>chng 11 dec 16, from 3.6 to 3.835, adjust botches due to recent iso recomb changes
monitor line "H  1" 6563 3.835
//
// >>chng 07 oct 22, from 1.00 to 1.30, resolve l-levels of h-like sequence 
// >>chng 08 apr 10, from 1.30 to 1.38, change default h-like levels, other minor changes
monitor line "H  1" 4861 1.38
//
// >>chng 07 oct 22, from 0.589 to 0.640, resolve l-levels of h-like sequence 
// >>chng 11 dec 16, from 0.64 to 0.6822, adjust botches due to recent iso recomb changes
monitor line "H  1" 4340 0.6822
monitor line "H  1" 4102 0.378
// >>chng 07 mar 13, from -3.225 to -3.250, change in lines_service to fix cache errors
// >>chng 07 jun 25, from -3.250 to -3.295, move h-like treatment to he-like methods.
// >>chng 07 oct 22, from -3.295 to -3.341, resolve l-levels of h-like sequence 
// >>chng 11 dec 16, from -3.341 to -3.308, adjust botches due to recent iso recomb changes
monitor hydrogen 1 ionization -3.308
c limit_casea_h_den13.in
c class limit 
c ========================================
c 

Case A is a mathematical fiction; when the Lyman lines are
optically thin continuum pumping must be important if the gas
is ionized.  Fluorescence is turned off with the
no induced processes command.  The density is set to a
very high value (1015 cm-3) so that the 2s-2p states are well l-mixed,
in keeping with standard case A assumptions.  As a result,
collisional excitation would dominate the level populations,
and hydrogen collisions must be turned off with the hydrogen collisions off
command.  The Ly* optical depth is set to a small value.
The set dr command sets the zone thickness to 1 cm.
The abundances are set to a very small value so that the
electron density is equal to the hydrogen density. 
Checks:
-	Departure coefficients for H, He levels
-	Neutral fractions
-	H* emissivity

