function  lag_rate_rate_O_O2
% Evaluation of the rate coefficient for the O-O2 dissociation reaction
% with two Laguerre quadratures
format long e
temp=6000; kt=0.8617e-04*temp; yzero=14.5/kt;
for n=2:2:50
% Laguerre quadratures for alpha =1
[pt,wt] = lagptwt2(n,1);
[sig]=sigma_O_O2((pt+yzero)*kt);
rate1=sum(wt.*sig);
% Laguerre quadratures for alpha = 0
[pt,wt] = lagptwt2(n,0);
[sig]=sigma_O_O2((pt+yzero)*kt);
rate2=sum(wt.*sig);
rate=1e12*(exp(-yzero)*rate1+yzero*exp(-yzero)*rate2);
fprintf('%i %16.6f %16.6f %12.6f\n',n,rate1,rate2,rate)
end
% Reactive cross seciton
function [sig]=sigma_O_O2(e)
n=length(e);
for i=1:n
sig(i)=4.51*(e(i)-14.5)^1.03/(0.21+e(i)^1.31);
end
% Laguerre quadratures
function [pt,wt] = lagptwt2(n,alf)
format long e
xn=[0:1:n-1]; a=2*xn+alf+1; b=(xn.*(xn+alf));
rtb=sqrt(b); rtb(1)=[];
t=diag(rtb,-1)+diag(a)+diag(rtb,1);
[f,lambda]=eig(t);
pt=diag(lambda);
wt=gamma(alf+1)*f(1,:).^2; 
ptwt=[pt,wt'];