FINE STRUCTURE OF THE SCHUMANN-RUNGE BANDS NEAR THE CONVERGENCE LIMIT AND THE DISSOCIATION ENERGY OF THE OXYGEN MOLECULE

Abstract

The Schumann-Runge absorption bands of O2[Formula: see text] have been photographed in the fourth order of a 3 m. vacuum spectrograph with a resolution of 160,000. Some spectra were taken with the O2 at liquid air temperature. A detailed line structure analysis has been carried out for all bands with ν′ > 11. In addition to the six main branches (with ΔJ = ΔN = ± 1), for low values of the quantum number N (total angular momentum apart from spin), several lines of the six satellite branches [Formula: see text] as well as of the two "forbidden" branches (with ΔN = ± 3, ΔJ = ± 1) have been identified. Values of the rotational constants and the vibrational quanta in the upper state have been derived up to ν′ = 21. The triplet splitting increases rapidly with N and with ν′; it cannot be described accurately by the known theoretical formulae.The origin of the 21–0 band is at 57115 cm−1. A very short extrapolation gives the convergence limit at 57128 ± 5 cm−1. This limit agrees excellently with the one derived from the near ultraviolet [Formula: see text] bands if it is assumed that at both limits those O atoms that are produced in the 3P state are in the lowest component level of this state, viz. 3P2. A discrepancy pointed out earlier by Herzberg is thus removed. The convergence limit just mentioned and certain other data derived from the spectrum lead to very precise information about the dissociation energy of O2. Without any extrapolation the dissociation energy into normal atoms can be given as 41260 ± 15 cm−1 (or 5.1148 ± 0.002 ev. or 117.96 ± 0.04 kcal./mole), which is 0.63% higher than the old value.