title generate standard ISM opacity curve
c
c commands controlling continuum =========
table agn
ionization parameter -3
c
c commands for density & abundances =========
hden 0 //set density of unity so that total opacity is per hydrogen atom
abundances ism no grains //this turns on depleted gas-phas abundances
grains no qheat
c
c commands controlling geometry  =========
set dr 0
stop zone 1
c
c other commands for details     =========
iterate
c
c commands controlling output    =========
save overview "ism_opacity.ovr"
save performance "ism_opacity.per"
save total opacity last "ism_opacity.opc" units kev
c
c commands giving the monitors    =========
// >>chng 02 jun 15, all entries converted to luminosity since Hb changed
// >>chng 07 oct 22, from -24.833 to -24.892, resolve l-levels of h-like sequence
monitor line "totl" 4861 intensity -24.892
// 
// >>chng 01 feb 20, from 9070 to 10075 when default ISM O abundance changed
monitor temperature hydrogen 2 10075
// 
monitor line "ca b" 4861 intensity -24.856
// 
// >>chng 01 feb 20, from 1.461 to 1.227 when default ISM O abundance changed
// >>chng 06 nov 29, from -24.594 to -24.619, Badnell DR turned on
monitor line "totm" 0  intensity -24.619
// 
// >>chng 01 feb 20, from 1.007 to 1.166 when default ISM O abundance changed
// >>chng 02 may 27, from 1.166 to 1.062, improved gaunt factors
// >>chng 02 jun 21, from -24.660 to -24.698 improved gaunt factors
monitor line "h ff" 0  intensity -24.698
// 
// >>chng 02 jun 21, from -24.562 to -24.603 improved gaunt factors
monitor line "toff" 0  intensity -24.603
// 
// >>chng 01 feb 20, from 0.9766 to 1.076 when default ISM O abundance changed
// >>chng 01 mar 07, from 1.08 to 0.902 change in grain physics
// >>chng 03 jan 12, from -24.727 to -24.642, new grains
// >>chng 07 dec 15, from -24.642 to -24.820, X-ray grain merge
monitor line "grgh" 0  intensity -24.820
// 
// >>chng 01 feb 20, from 0.3728 to 0.459 when default ISM O abundance changed
// >>chng 01 mar 07, from 0.459 to 0.391 change in grain physics
// >>chng 03 jan 12, from -25.084 to -25.062, new grains
// >>chng 05 jul 05, from -25.062 to -25.070, fine tune
monitor line "grgc" 0  intensity -25.070
// 
// >>chng 01 feb 20, from 0.3158 to 0.244 when default ISM O abundance changed
monitor line "ct h" 0  intensity -25.299
// 
save monitors last "ism_opacity.asr"
c ism_opacity.in
c class limit 
c ========================================
c 

This example creates the file ism_opacity.opc which tabulates
the total opacity of the gas as a function of energy.  These
plots are used in ISM studies to understand the transmission
characteristics along a line of sight.  The opacity depends on 
the dust to gas ratio, the gas phase abundances, and the level
of ionization, all of which can be changed by altering parameters
given above.

The model is of a 1 cm think parcel of gas which is optically thin 
in the Lyman continuum and Lyman lines.  As a result the hydrogen
emission line spectrum is close to case C.  The model iterates
so that the predicted ionization and emission know about this.