Comets: Production Mechanisms of Hydroxyl and Hydrogen Halos

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Science  11 Jun 1971:
Vol. 172, Issue 3988, pp. 1126-1127
DOI: 10.1126/science.172.3988.1126


The brightness dependence on the heliocentric distance that has been observed for the hydrogen and the hydroxyl halos of comet 1969g can be quantitatively explained by a three-step process: the vaporization of the water snows, the photodissociation of the water molecule into the ground states of hydrogen and hydroxyl, and the photoexcitation of hydrogen and hydroxyl by a fluorescence mechanism.