Emission spectra of RuN have been recorded at high resolution in the region 12 000–35 000 cm−1 using a Fourier transform spectrometer. The molecules were excited in a ruthenium hollow cathode lamp in the presence of about 2.5 Torr of Ne and 5 m Torr of N2. New bands with origins near 17 758.1, 18 866.4, 19 800.4 and 20 721.5 cm−1 have been assigned as the 0–1, 0–0, 1–0, and 2–0 bands of a new 2Σ+–2Σ+ system with the lower state as the ground state. This transition has been labeled as F2Σ+–X2Σ+, with the F2Σ+ state arising from the 1σ22σ21π41δ44σ1 configuration. A rotational analysis of these bands has been carried out and spectroscopic constants have been extracted. The principal equilibrium constants for the ground state of RuN are ΔG(1/2)″=1108.3235(22) cm−1, Be″=0.5545023(42) cm−1, αe″=0.0034468(57) cm−1, re″=1.5714269(60) Å, while the equilibrium constants for the excited state are ωe′=946.8471(40) cm−1, ωexe′=6.4229(14) cm−1, Be′=0.50085(21) cm−1, αe′=0.00375(10) cm−1, re′=1.65345(34) Å. This transition is analogous to the E2Σ+–X2Σ+ system of RhC (W. J. Balfour et al., J. Mol. Spectrosc.198, 393 (1999)).