Knowledge Bank

The absorption spectrum of nitrogen has been investigated with a 6.5 m vacuum spectrograph in the 650--1000 \AA region. Rotational analyses of six bands belonging to the system, the upper state of which is the lowest member of the Rydberg series converging to A $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi u$ of $N2+$, were carried out and yielded accurate rotational constants for each vibrational level. Rotational perturbations observed in the system will be discussed.