In the region 250-550 nm, the spectrum can be adequately described by the semi-empirical function (eqn. 12)

σ(λ,T) = 2.73×10^-19 cm² x tanh^0.5
× exp{-99.0 x tanh x [ln(329.5 nm/λ)]²}
+ 9.32×10^-21 cm² x tanh^0.5
× exp{-91.5 x tanh x [ln(406.5 nm/λ)]²}

with tanh = tanh(hcX559.751 cm^-1/2KT) = tanh(402.7/T);
λ in nm, 250 < λ < 550 nm, and T in K; 300 K > T > 195 K

The absorption cross sections have been calculated at 0.2-nm intervals using this formula