title test H and He ionization in optically thin limit
c
c commands controlling continuum =========
laser 4.3 Ryd
phi(h) 10
c
c commands for density & abundances =========
hden 1
abundances all -10
c
c commands controlling geometry  =========
stop zone 1
set dr 0
c
c other commands for details     =========
iterate  to convergence 
constant temperature = 4
c
c commands controlling output    =========
save overview "limit_laser_3.ovr"
save performance "limit_laser_3.per"
save monitors "limit_laser_3.asr" last
c
c commands giving the monitors    =========
monitor ionization hydrogen 1 -2.37
monitor ionization helium   1 -6.32
monitor ionization helium   2 -2.77
monitor niter 3 error 0.01
c limit_laser_3.in
c class limit 
c ========================================
c 

This checks the calculation of the hydrogen and helium photoionization
equilibrium.  The continuum is a laser peaked at 4.3 Ryd, where it
can fully ionize both hydrogen and helium. 

Checks:
-	The hydrogen neutral fraction is nearly 4.18*10-4
	(not exact since laser has finite width).
-	Helium ion: The ratio He+/He++ should be 1.69*10-3 and
	the ratio Heo/He+ should be 2.86*10-4.
-	Hb emissivity should be close to high-density case A.  The predicted
	TOTL 4861 intensity should be nearly 2.2 times the expected
	case B intensity.

H cross section is 1.0E-18 cm^2, rec coef is 4.18E-13
answer is n(Ho)/n(H+)=4.18e-3
HeI cross section is 1.51E-18 cm^2, rec coef is 4.32e-13
answer is n(Heo)/n(He+)=2.86e-4, so Heo/He = 4.83e-7
HeII cross section is 1.30E-18 cm^2, rec coef is 2.20e-12
answer is n(He+)/n(He2+)=1.69e-3
