Roberts, E. H.Nixon, K. L.Dedman, C. J.Gibson, S. T.Lewis, B. R.2015-10-212015-10-210021-9606http://hdl.handle.net/1885/15989Through the use of isotopically pure gas at a temperature of 77 K, a weak photoabsorption band of ¹⁶O₂ is found near 1856 Å, underlying the stronger Schumann–Runge (SR) band B³Σ−u←X³Σ−g(8,0). The location, structure, and intensity of this new band are consistent with expectation for the magnetic dipole transitionB′ ³Πg←X³Σ−g(0,0), where the designation B′ is chosen to represent the II ³Πg valence state. This electronic transition contributes to the “excess absorption” underlying the SR bands [B. R. Lewis, S. T. Gibson, and E. H. Roberts, J. Chem. Phys. 115, 245 (2001)].http://www.sherpa.ac.uk/romeo/issn/0021-9606..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 20/10/15). Copyright 2002 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics and may be found at https://doi.org/10.1063/1.1456506Keywords: Electron transitions; Electrostatics; Light absorption; Molecular structure; Monochromators; Oxygen; Photomultipliers; Photons; Potential energy; Ultraviolet radiation; Diatomic molecules; Magnetic dipole transitions; Band structure2002-04-0110.1063/1.14565062015-12-11