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/* This file is part of Cloudy and is copyright (C)1978-2008 by Gary J. Ferland and
 * others.  For conditions of distribution and use see copyright notice in license.txt */
/*atmdat_DielSupres derive scale factors for suppression of Burgess dielectronic recombination */
#include "cddefines.h"
#include "ionbal.h"
#include "dense.h"
#include "phycon.h"
#include "punch.h"
#include "atmdat.h"

/* >>chng 07 feb 28 by Mitchell Martin, added new dr suppression routine */
/* This function computes the standard electron density-dependent
 * suppression factor of the DR rate coefficient of the C3+ ion 
 * at T = 10^5 K, based on Nigel Badnell's 1993 ApJ paper.
 * It is then scalable for other choices of ionic charge and temperature.
 */
//#define USENEW
#ifdef USENEW
STATIC double dr_suppress(
        /* This routine takes the following arguments:
         * atomic_number = nuclear charge */
        long int atomic_number, 
        /*ionic_charge = ionic charge*/
        long int ionic_charge, 
        /*eden = electron density */
        double eden, 
        /*T = temperature (K)*/
        double T )
{


        /* fitting constants to compute nominal suppression factor function */
        const double A = 12.4479;       /* various fitting parameters follow */
        const double mu = 0.46665;
        const double w = 4.96916;
        const double y_c0 = 0.5498;     /* log10 of the electron density fitting parameter for C3+ */

        /* Nigel's 1993 ApJ paper computed the DR rate as a function of log n_e
         * at a temperature T = 100,000 K.
         */
        const double T_0 = 1.e5;        /* the standard temperature in Nigel's original C3+ fit */
        const double q_0 = 3.;          /* the ionic charge of C3+, addressed in Nigel's paper */

        /* a fitting constant to compute the suppression factor corrected for an
         * estimate of surviving DR based on the lowest dipole allowed core
         * excitation energy
         */
        const double c = 3.0;   /* smaller c means larger fraction will survive, and vice versa */

        double s, snew, y_c, E_c, E_c0, x, g_x;
        long int iso_sequence;

        eden = log10(eden);
        iso_sequence = atomic_number - ionic_charge;    /* the isoelectronic sequence number, iso_sequence=3 for Li-like, etc */

        y_c = y_c0 + log10( pow( (ionic_charge/q_0), 7. ) * sqrt( T/T_0 ) );

        /* here we compute the standard suppression factor function, s( n_e, T, ionic_charge ) */
        if( eden >= y_c )
        {
                s = (A/(PI*w)) * ( mu/( 1. + pow((eden-y_c)/w, 2.) ) + 
                    (1. - mu) * sqrt(PI*LN_TWO) * exp( -LN_TWO * 
                    pow((eden-y_c)/w, 2.) ) );
        }
        else
        {
                s = (A/(PI*w)) * ( mu + (1.- mu) * sqrt(PI*LN_TWO) );
        }

        /* Now we're going to modify this standard suppression factor curve to
         * allow for the survival of some fraction of the total DR rate at
         * generally lower temperatures T, when appropriate.
         */

        /* Computational estimates of lowest dipole allowed core excitation
         * energies for various iso-electronic sequences of recombining ion;
         * these are fits to NIST statistical weighted energies
         */
        if( iso_sequence == 3 ) /* Li-like ions */
        {
                E_c = 2.08338 + 19.1356*(ionic_charge/10.) + 0.974 *
                      pow( ionic_charge/10., 2. ) - 0.309032*pow( ionic_charge/10., 3. ) +
                      0.419951*pow( ionic_charge/10., 4. );
        }
        else if( iso_sequence == 4 ) /* Be-like ions */
        {
                E_c = 5.56828 + 34.6774*(ionic_charge/10.) + 1.005 *
                      pow( ionic_charge/10., 2. ) - 0.994177*pow( ionic_charge/10., 3. ) +
                      0.726053*pow( ionic_charge/10., 4. );
        }
        else if( iso_sequence == 7 ) /* N-like ions */
        {
                E_c = 10.88361 + 39.7851*(ionic_charge/10.) + 0.423 *
                      pow( ionic_charge/10., 2. ) - 0.310368*pow( ionic_charge/10., 3. ) +
                      0.937186*pow( ionic_charge/10., 4. );
        }
        else if( iso_sequence == 11 ) /* Na-like ions */
        {
                E_c = 2.17262 + 22.5038*(ionic_charge/10.) - 1.227*pow( ionic_charge/10., 2. ) +
                      0.801291*pow( ionic_charge/10., 3. ) +
                      0.0434168*pow( ionic_charge/10., 4. );
        }
        else if( iso_sequence == 1 || iso_sequence == 2 || iso_sequence == 10 )
        {
                /* set to a very large number to force suppression factor to 1.0
                 * for H, He, Ne-like ions */
                E_c = 1.e10;
        }
        else
        {
                /* specifically B, C, O, or F-like ions (iso_sequence = 5, 6, 8, 9) */
                E_c = 0.0;      /* forces suppression factor to s for all T */
                /* iso_sequence.B. ion sequences beyond Na-like, iso_sequence > 11, are currently not
                 * treated */
        }

        /* the lowest dipole allowed energy for Li-like C3+, atomic_number = 6, iso_sequence = atomic_number-ionic_charge = 3 */
        E_c0 = 2.08338 + 19.1356*(q_0/10.) + 0.974 * 
               pow( (q_0/10.), 2. ) - 0.309032 * 
               pow( (q_0/10.), 3. ) + 0.419951 *
               pow( (q_0/10.), 4. );

        /* and important factor that determines what survives */
        x = ( (E_c*EVDEGK)/(c*T) - (E_c0*EVDEGK)/(c*T_0) );

        if( x > 1 )
        {
                g_x = x;
        }
        else if( x >= 0 && x <= 1 )
        {
                g_x = x*x;
        }
        else
        {
                g_x = 0.0;
        }

        /* converting the standard curve to the revised one allowing for
         * survival at lower energies
         */
        snew = 1. + (s-1.)*exp(-g_x);

        return snew;
        ASSERT( snew >=0. && snew <= 1. );
}
#endif

void atmdat_DielSupres(void)
{
        long int i;

        DEBUG_ENTRY( "atmdat_DielSupres()" );

        /* dielectronic burgess recombination suppression, default is true */
        if( ionbal.lgSupDie[0] )
        {
                for( i=0; i < LIMELM; i++ )
                {
#                       ifdef USENEW
                        ionbal.DielSupprs[0][i] = (realnum)dr_suppress( i+1, 3, dense.eden, phycon.te );
#                       else
                        /* effective density for scaling from Davidson's plot
                         * first do temperature scaling, term in () is SQRT(te/15,000) */
                        double effden = dense.eden/(phycon.sqrte/122.47);

                        /* this is rough charge dependence, z^7 from Davidson */
                        effden /= powi((realnum)(i+1)/3.,7);

                        ionbal.DielSupprs[0][i] = (realnum)(1.-0.092*log10(effden));
                        ionbal.DielSupprs[0][i] = (realnum)MIN2(1.,ionbal.DielSupprs[0][i]);
                        ionbal.DielSupprs[0][i] = (realnum)MAX2(0.08,ionbal.DielSupprs[0][i]);
#                       endif
                }
        }

        else
        {
                for( i=0; i < LIMELM; i++ )
                {
                        ionbal.DielSupprs[0][i] = 1.;
                }
        }

        /* nussbaumer and storey recombination
         * default is this to be false */
        if( ionbal.lgSupDie[1] )
        {
                for( i=0; i < LIMELM; i++ )
                {
                        /* assume same factors as above */
                        ionbal.DielSupprs[1][i] = ionbal.DielSupprs[0][i];
                }
        }
        else
        {
                for( i=0; i < LIMELM; i++ )
                {
                        ionbal.DielSupprs[1][i] = 1.;
                }
        }

        /* option to punch recombination coefficients, set with *punch recombination 
         * coefficients* command*/
        if( punch.lgioRecom )
        {
                fprintf( punch.ioRecom, " atmdat_DielSupres finds following dielectronic"
                        " recom suppression factors.\n" );
                fprintf( punch.ioRecom, "  Z    fac \n" );
                for( i=0; i < LIMELM; i++ )
                {
                        fprintf( punch.ioRecom, "%3ld %10.3e %10.3e\n", i+1, 
                          ionbal.DielSupprs[0][i], ionbal.DielSupprs[1][i] );
                }
                fprintf( punch.ioRecom, "\n");
        }
        return;
}

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