High-resolution VUV absolute photo-absorption cross sections of N2 and rare gases

Abstract

We present absolute total photoabsorption cross sections measured with the Very High Resolution Spectrometer at the SURF-II synchrotron radiation source at the National Institute of Standards and Technology, with a resolution of 9 mÅ at 835 Å in the first order. The cross sections of N2 at the wavelengths of the OΠ(2s2p4-4P2s22p3 4S) multiplet are found to be 10 Mb at 834.467 Å, 0.3 Mb at 833.332 Å, and 0.05 Mb at 832.862 Å. This new high-resolution measurement confirms the 10 Mb value, which has given rise to some still-unsolved discrepencies in interpreting atmospheric observations of the OΠ emission.1 We also measure absolute cross sections in the continua of rare gases, including the argon 3s3p6np absorption windows at 425 Å.