title test of H ionization in optically thin limit
c
c commands controlling continuum =========
laser 1.5 Ryd 
phi(h) 10
c
c commands for density & abundances =========
hden 1
init file="hheonly.ini"
c
c commands controlling geometry  =========
set dr 0
stop zone 1
c
c other commands for details     =========
constant temperature = 4
iterate to convergence
c
c commands controlling output    =========
save overview "limit_laser_1.ovr"
save performance "limit_laser_1.per"
save monitors "limit_laser_1.asr" last
save convergence reason "limit_laser_1.cvr"
c
c commands giving the monitors    =========
monitor ionization hydrogen 1 -3.699
monitor niter 3 error 0.01
c limit_laser_1.in
c class limit 
c ========================================
c 

This checks the calculation of the hydrogen photoionization equilibrium.
The continuum is a laser peaked at 1.5 Ryd, where the hydrogen
photoionization cross section is 2.09*10-18 cm-2. 

Checks:
-	The hydrogen neutral fraction is nearly 2.00*10-4 (not exact
	since laser has finite width).
-	Hb emissivity 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 2.09E-18 cm^2, rec coef is 4.18E-14
answer is neutral fraction 2.00E-4
also checks that only 3 iterations needed