High-temperature ultrahigh-resolution absorption cross-section measurements of O2 in the EUV region

The high-resolution absorption cross-section measurements of O2 in the extreme ultraviolet region have been carried out using a 0.0008 nm resolution and at temperatures of 295 and 535 K. The photon wavelength regions were selected to coincide with the most prominent EUV solar emission features, namely, the N II 108.5 nm, the N II 91.7 nm, the O I 91.1 nm, the O II 83.4 nm, and the He II 30.4 nm. The absorption features of O2 in the extreme ultraviolet region are known to be quite diffuse, therefore the cross-section values of O2 in this spectral region will not critically depend upon the resolution. As the temperature increases from 295 to 535 K we observed that the cross-section value can increase by as much as 60% and decrease by as much as 35% in the presently selected wavelength regions.