See "V S S Chan 1999" PhD thesis for explanation of the code

Appendix



#include "stdio.h"
#include "math.h"
#define B_cont 2.5824e12
#define wave_length 5145.0
#define molar_mass 254.000
#define Mega_heltz 1e+6




main() /*This routine calculates the iodine absorption profile of the P13/R15 line system at 514.5nm*/
{

FILE *fopen(),*fp1;
int freq_loop1,freq_loop2;
float alf_length;
float absorb_coeff,trans1,temp;
double absorb_cont,cnst1,cnst2,thermal_line,trans2,fact1,fact2,fact3,fact4,freq_offset1,freq_offset2;
char fname[50];

printf("\n This program calculates the iodine absorption profile P13/R15 line system (514.5nm)");
printf("\n Written by Victor Chan 25/2/95");
printf("\n\n\n");
printf("\n Enter filename to save the calculated data in\n");
gets(fname);
fp1=fopen(fname,"w");

printf("\n Input the length of the absorption line filter (ALF) in cm\n ");
scanf("%f",&alf_length);

printf("\n Input cell wall temperature of the ALF in degree C\n");
scanf("\n%f",&temp);

fprintf(fp1,"\n Iodine absorption profile calculation");

fprintf(fp1,"\n Length of the ALF = %f  cm",alf_length);
fprintf(fp1,"\n Cell wall temperature of the ALF = %f degree C",temp);
trans1 = (41-temp)/40;        /* calculates the transmission at resonance using linear scaling*/ 
			      /* using 40 as the cut off point, according to Komine*/
 */
	if(temp>41)           /* absorption coefficent at the line centre is a function of temperature */
	{
		trans1 = 0.001;  /* assign a transmission value to prevent a negative value  */
	}
temp = temp+273.14;                                /* this model is from Miles et al 1991      */
						   /* Instanstanous filtered Rayleigh scattering....*/
printf("\n temperature of the cell is %f k",temp);
printf("\n length of the ALF is %f cm",alf_length);
absorb_coeff = -(log(trans1)/alf_length);
absorb_cont = absorb_coeff*alf_length;
cnst1 = 2*(temp/molar_mass);
cnst2 = sqrt(cnst1);
thermal_line = (1/wave_length)/cnst2*B_cont;
fprintf(fp1,"\n absorption constant at iodine molcular resonance =  %f ",absorb_cont);
for(freq_loop1=100;freq_loop1>0;freq_loop1--)

	{                                             /* this loop calculates the low frequency side */
		freq_offset1 = freq_loop1*10;
		freq_offset1 = freq_offset1*Mega_heltz;
		fact1 = freq_offset1/thermal_line;
		fact2 = fact1*fact1;
		fact3 = exp(-fact2);
		fact4 = absorb_cont * fact3;
		trans2 = exp(-fact4);
		freq_offset1 = freq_offset1*1.75;  /* this simulates the broadening of frequency */
		fprintf(fp1,"\n %f %f",-freq_offset1/Mega_heltz,trans2*100);
	}
for(freq_loop2=0;freq_loop2<101;freq_loop2++)

	{
		freq_offset2 = freq_loop2*10;            /* this loop calculates the high frequency side */
		freq_offset2 = freq_offset2*Mega_heltz;
		fact1 = freq_offset2/thermal_line;
		fact2 = fact1*fact1;
		fact3 = exp(-fact2);
		fact4 = absorb_cont * fact3;
		trans2 = exp(-fact4);
		freq_offset2 = freq_offset2*1.45;
		fprintf(fp1,"\n %f %f",freq_offset2/Mega_heltz,trans2*100);
	}

fclose(fp1);

}