#include <iostream>
#include <math.h>
#include <fstream>

int atmo(){

Double_t X0= 1013.;
Double_t XM = 0.01;
Double_t n0= 0.00029;
Double_t dx=0.01;
Double_t n;
Double_t H0 = 8.4e3;

TH1D *h1= new TH1D("h1","",200,0.,200.); 
TH1D *h2= new TH1D("h2","",200,1.,log(200.)); 

Double_t z;
Double_t sc2;
Double_t sc;
Double_t y;
Double_t phot=0.;
for (Double_t x = XM; x <=X0; x+=dx){
n = 1.+n0*x/X0;
z = -H0*log(x/X0)-2400.;
sc2 = 1.-1./n**2;
sc = sqrt(sc2);
y = sqrt(n**2-1.)*z;
if(z>0){
phot = 2.*acos(-1.)/137.*sc2*(1./400.e-9-1./700.e-9)/2./acos(-1.)/y;
h1->Fill(y,phot);
h2->Fill(log(y),phot);
}

}
TCanvas *c1 = new TCanvas("c1");
c1->SetLogy();
h1->Draw();
TCanvas *c2 = new TCanvas("c2");
c2->SetLogy();
h2->Draw();
}