cloudy: /home66/gary/public_html/cloudy/c08_branch/source/atom

00001 /* This file is part of Cloudy and is copyright (C)1978-2008 by Gary J. Ferland and
00002  * others.  For conditions of distribution and use see copyright notice in license.txt */
00003 /*atom_pop3 solve 3-level atom without radiative transfer, returns pops of level 2 and 3 */
00004 #include "cddefines.h"
00005 #include "phycon.h"
00006 #include "dense.h"
00007 #include "atoms.h"
00008 
00009 /*atom_pop3 return value is population for 3-level atom, cm^-3 */
00010 double atom_pop3(
00011         /* statictical weights of levels 1, 2, and 3 */
00012         double g1, double g2, double g3, 
00013 
00014         /* collision strengths between three levels */
00015         double o12, double o13, double o23, 
00016 
00017         /* transition probabilities between three levels */
00018         double a21, double a31, double a32, 
00019 
00020         /* excitation energy in Kelvin */
00021         double Tex12, double Tex23, 
00022 
00023         /* returned population of level 2, cm^-3 */
00024         realnum *pop2, 
00025 
00026         /* incoming total abundance of ion */
00027         double abund, 
00028 
00029         /* possible photodestruction of level 2, normally 0 */
00030         double gam2,
00031 
00032         /* excitation rates (s-1) due to "other" processes,
00033          * these are not included in the energy exchange */
00034         double r12, 
00035         double r13 )
00036 {
00037         double alf, 
00038           b12, 
00039           b13, 
00040           b23, 
00041           bet, 
00042           c21, 
00043           c23, 
00044           c31, 
00045           c32, 
00046           ex, 
00047           fac, 
00048           pop3_v;
00049 
00050         DEBUG_ENTRY( "atom_pop3()" );
00051 
00052         /* computes level populations for 3 level atom, all col rad coupling
00053          * results are populations of levels 2 and 3, (cm^-3) no A included */
00054         ex = Tex12/phycon.te;
00055         if( (abund <= 0.) || (ex > 20. && r12<SMALLFLOAT ) )
00056         {
00057                 pop3_v = 0.;
00058                 *pop2 = 0.;
00059                 return( pop3_v );
00060         }
00061 
00062         /* confirm that these are sane values */
00063         ASSERT( g1>0. && g2>0. && g3>0. && o12>=0. && o13>=0. && o23>=0. && a21>=0. && a31>=0. && a32>=0. && 
00064                 Tex12>=0. && Tex23>=0. );
00065 
00066         b12 = exp(-ex);
00067         b23 = exp(-Tex23/phycon.te);
00068 
00069         b13 = b12*b23;
00070         if( b13 == 0. && r12<SMALLFLOAT )
00071         {
00072                 pop3_v = 0.;
00073                 *pop2 = 0.;
00074                 return( pop3_v );
00075         }
00076 
00077         /* these rates have units s-1 */
00078         atoms.c12 = dense.cdsqte*o12/g1*b12 + r12;
00079         atoms.c13 = dense.cdsqte*o13/g1*b13 + r13;
00080         c23 = dense.cdsqte*o23/g2*b23;
00081         c32 = dense.cdsqte*o23/g3;
00082         c31 = dense.cdsqte*o13/g3;
00083         c21 = dense.cdsqte*o12/g2;
00084 
00085         alf = a21 + c21 + c23 + gam2;
00086         bet = a31 + a32 + c31 + c32;
00087         *pop2 = (realnum)((atoms.c13/bet + atoms.c12/(c32 + a32))/(alf/(c32 + a32) - c23/bet));
00088         pop3_v = (atoms.c13 + *pop2*c23)/bet;
00089 
00090         /* renorm to 1+pop2+atom_pop3=1 */
00091         fac = abund/(1. + *pop2 + pop3_v);
00092         *pop2 *= (realnum)fac;
00093         pop3_v *= fac;
00094 
00095         return( pop3_v );
00096 }
/home66/gary/public_html/cloudy/c08_branch/source/atom_pop3.cpp
