Abstract
THE light emitted by the night sky is a remarkable afterglow associated with recombination of atomic oxygen in the upper atmosphere1. Two normal atoms of oxygen could not recombine with emission of light; the recombination occurs only in presence of a third body to satisfy the principles of conservation. If that third body is an oxygen atom 3P, it can attain the level 1S by the following process: O(3P) + O(3P) + O(3P)→O2(X, υ= 5) + O(1S). The total energy absorbed by the vibrations of the molecule and by the excitation of the atom (0·93 + 4·18 = 5·11 volts) agrees closely with the energy supplied by the recombination. Thus can be explained the emission of lines λλ 5577–6300 by the night sky. But if the third body is a nitrogen molecule in the normal state, the available 5·09 volts is insufficient to excite it, and we have to consider the three-body collision : O(3P)+O(1D)+N2(X)→O2(X,υ2)+N2(A, υ2). In such a collision the energy made available is D= 7·05 volts ; hence the possibility must be considered of emission of Vegard-Kaplan bands N2(A→X). Only those bands the upper level of which does not exceed 7·05 volts will be emitted, and the corresponding quantum number υ2 is at most equal to 5.
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References
Chapman, Phil. Mag., 10, 369 (1930) and 23, 657 (1937).
Kaplan, Phys. Rec., 31, 997 (1928).
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CABANNES, J., AYNARD, R. Mechanism of Nitrogen Excitation in the Night Sky. Nature 144, 442 (1939). https://doi.org/10.1038/144442a0
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DOI: https://doi.org/10.1038/144442a0
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