function sigma_O_O2
clc
% Energy dependence of the reactive cross section for O-O_2 dissociation
% First energy interval up to the htreshold energy 14.5 eV. Fig. 3.7
e=[]; e1=[0:.2:14.5]; e=[e e1]; n1=length(e); 
sigr=0*(1:1:n1); sigloc=0*(1:1:n1);
% Second energy interval above the threshold energy
e2=[15:.2:50]; n2=length(e2);
for i=1:n2
sig2(i)=4.51*(e2(i)-14.5)^1.03/(0.21+e2(i)^1.31);
sigloc2(i)=1.8*(1-14.5/e2(i));
end
e=[e e2];sigr=[sigr sig2]; sigloc=[sigloc sigloc2];
%for i=1:n
%fprintf('%12.4f %13.5e\n',e(i),sigr(i))
%end
plot(e,sigr,'-k','linewidth',1.2)
hold on
plot(e,sigloc,'--k','linewidth',1.2)
axis([0 50 0 1.4])
set(gca,'FontSize',20)
set(gca,'Ytick',[0:.2:1.4],'linewidth',1.6)
set(gca,'Xtick',[0:10:50],'linewidth',1.6)
xlabel('$E (eV)$','Interpreter','LaTex','FontSize',24)
ylabel('$\sigma_r(E)(\AA^2)$','Interpreter','LaTex','FontSize',24)
hold off