On the proposals of Chapman and of Barth for O(1S) formation in the upper atmosphere

It is argued that Chapman's process is too slow to explain the green line emission in the nightglow but that Barth's two-stage mechanism is fast enough. The key to the difference in their efficiencies is that the life-time of Chapman's intermediate [O₃] complex is very much shorter than that of Barth's intermediate [O₃] complex because of its greater internal energy. Consequently the chance of the representative mass point passing from the initial surface to the required final surface is very much less in the former case than the latter where O(¹S) is one of the products in a quite considerable fraction of the decays of the complex.