The Herman-Kaplan system of N 2: High resolution studies

The Herman-Kaplan system of N ₂ has been observed for the first time under high resolution and rotational analyses of four bands have been carried out. It is shown that the upper state, E, is of species of ³Σ_g⁺ with a rotational constant B₀, of 1.927 ₃ cm ^-1 and a T₀ value of 95 774.50 cm ^-1. No spin splitting is detected in the E state within the limits of experimental error. The results establish that the state is, as proposed by Mulliken, the ³Σ_g⁺ state obtained by the addition of a 3 sσ_g Rydberg electron to the X ²Σ_g⁺ ground state of N ₂⁺. The data for the lower state are in good agreement with those which have been derived from studies of the first positive system.