Emission Band Spectra of Nitrogen. Kaplan's First and Second Systems

Seven bands of Kaplan's first system and eleven bands of Kaplan's second system have been photographed under high resolution. The two systems are definitely y1Π−a′1 Σ and y 1Π−w1Δ. It is very probable that they are y 1Πg−a′1Σu− and y 1Πg−w 1Δu and that the two lower states belong, along with A 3Σu+ and b′1Σu+, to the N2 configuration ··· πu3σg2πg. A clear breaking-off of the branches coming from the Π+ levels of the y 1Πg state above v′=0,J′=10 was observed. This is interpreted as an allowed predissociation by a Σg+1 state dissociating to two 2D atoms. Consequently lower limits probably close to the term values for the x, y, w, and a′ states could be determined; this locates the a′ and w states respectively probably about 2.2 and 2.7 ev above state A, in good agreement with theoretical expectations. Perturbation of the remaining Π— levels was also observed. Rotational and vibrational constants and term values of the various states are presented. The transitions a′↔a and w↔a should give rise to bands in the (mostly far) infrared. It is noted that the constants of both the x and y states are close to those of the N2+ state ··· πu3σg2, and it is proposed that x1Σg— and y1Πg are respectively derived from the latter by the addition of an electron in a 3pπu and a σu (4pσu ?) Rydberg orbital. It is then proposed that the DΣu+3 and p′ Σu+1 states of N2, whose constants are close to those of the ground state ··· πu4σg of N2+, are derived from the latter by addition of an electron in the same σu Rydberg orbital as in the y state. The states p′ and e are the first two members of Worley's first Rydberg series.