PREDISSOCIATION AND DISSOCIATION OF THE N2 MOLECULE

Abstract

The predissociation in the upper state of the Lyman–Birge–Hopfield bands of nitrogen has been investigated under high resolution. A clear breaking-off of the fine structure has been found above ν′ = 6, J′ = 13 both in the P and the Q branches. The predissociation limit is at 78,843 ± 50 cm.−1 which is smaller than the well known dissociation limit 97,944 cm.−1 by very nearly the excitation energy of the 2D state of the N atom. This observation eliminates the intermediate value, 8.565 ev., for the dissociation energy of the N2 molecule. A definite decision between the two remaining values, 9.756 and 7.373 ev., cannot yet be made. Acceptance of the former would involve the assumptions that the predissociation in the a1Πg state is caused by the [Formula: see text] state resulting from normal atoms and that this [Formula: see text] state is not purely repulsive. The elimination of the value 8.565 ev. for D(N2) removes the value 7.50 ev. for D(CN) which has been fairly widely accepted.