title: Comets: production mechanisms of hydroxyl and hydrogen halos.
abstract: 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.
authors.forename: A H
authors.initials: AH
authors.lastname: Delsemme