/*ehe12p two photon emission from helium singlets */
#include "cddefines.h"
#include "splint.h"
#include "spline.h"
#include "ehe12p.h"
#define	NCRS	21

double ehe12p(double freq)
{
	double ehe12p_v, 
	  y;
	static double y2[NCRS];
	static double ener[NCRS]={0.,0.03738,0.07506,0.1124,0.1498,0.1875,
	  0.225,0.263,0.300,0.3373,0.375,0.4127,0.4500,0.487,0.525,0.5625,
	  0.6002,0.6376,0.6749,0.7126,0.75};
	static double crs[NCRS]={0.,5.03,8.09,10.16,11.52,12.52,13.25,13.70,
	  14.02,14.25,14.27,14.25,14.02,13.70,13.25,12.52,11.52,10.16,
	  8.09,5.03,0.};
	static int lgFirst = TRUE;

#	ifdef DEBUG_FUN
	fputs( "<+>ehe12p()\n", debug_fp );
#	endif

	if( lgFirst )
	{
		/* set up coefficients for spline */
		spline(ener,crs,NCRS,2e31,2e31,y2);
		lgFirst = FALSE;
	}

	if( freq < 0. || freq >= 1.56 )
	{
		ehe12p_v = 0.;
	}
	else
	{
		splint(ener,crs,y2,NCRS,freq/2.08,&y);
		ehe12p_v = y/2.16;
	}


#	ifdef DEBUG_FUN
	fputs( " <->ehe12p()\n", debug_fp );
#	endif
	return( ehe12p_v );
}