T in K cross section error limit at 447.7 nm 295 5.17e-18 1.01e-18 400 1.52e-18 3.10e-19 500 7.31e-19 1.41e-19 600 3.27e-19 6.80e-20 700 1.92e-19 4.30e-20 800 1.78e-19 4.40e-20