iloop=1;
XL=150;
XH=350;
dX=(XH-XL)/200;
X=linspace(150,350,200);
for iloop=1:length(X)
  [N6(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),6,-1,'nitrogen');
  [N16(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),16,-1,'nitrogen');
  [N8(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),8,-1,'nitrogen');
  [N17(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),17,-1,'nitrogen');
  [O11(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),11,-1,'oxygen');
  [O23(iloop),a2,a3,err]=diff_backscatter(355,X(iloop),23,-1,'oxygen');
  iloop=iloop+1;

endfor

Q_comb=(0.78*N17+0.21*O23);

plot(X,Q_comb)
hold on
plot(X,N17,'r')
plot(X,O23,'g')
