The band spectrum of nitrogen: new singlet systems

Five new systems due to N2 have been observed in a mildly condensed discharge through nitrogen. Rotational analyses of some of the bands have been made, and it is shown that all correspond to transitions to the a1Πu upper level of the Lyman-Birge-Hopfield System. An additional progression of the system studied by Van der Ziel, here referred to as the Fifth Positive System, has been found, necessitating a revision of the upper vibrational quantum numbers. Some of Kaplan’s systems have also been examined, and the rotational analysis of one shows that it corresponds to a transition to the lower level of the Fifth Positive System. This level very probably lies a little below a1Πu and must therefore be metastable; it may play an important part in the formation of active nitrogen. The rotational and vibrational constants for the singlet electronic states of N2 are tabulated.