function [sigma,dnu,dwave]=diff_backscatter_VR(wavelength)
frequency=1e7/wavelength;


% constants
h=6.62607015e-34;
hc=1.98644568e-25;
c=2.99792458e8;
k=1.380649e-23;

% rename variables
dnu=2330.7;
alpha=2.62e-14;
gamma=4.23e-14;
dwave=10000000/(frequency-dnu);

sigma=1e-10 * 16*(pi^4)*((frequency-dnu)^4)*(alpha+7*gamma/45)*h/(8*(pi^2)*c*dnu);
end