Fourier transform emission spectroscopy and ab initio calculations on OsN

The emission spectrum of OsN has been recorded in the 3000–13 000 cm−1 region using a Fourier transform spectrometer. OsN molecules were excited in an osmium hollow cathode lamp operated with neon gas and a trace of nitrogen. Six bands observed in the 8000–12 200 cm−1 region have been classified into three transitions, a 4Π5/2–X 2Δ5/2, b 4Φ7/2–X 2Δ5/2, and b 4Φ5/2–X 2Δ5/2 with the 0–0 band origins near 8381.7, 11 147.9, and 12 127.2 cm−1, respectively. A rotational analysis of these bands provides the following equilibrium constants for the ground electronic state: ωe=1147.9492(77) cm−1, ωexe=5.4603(36) cm−1, Be=0.493 381(55) cm−1, αe=0.002 753(38) cm−1, and re=1.618 023(91) Å. Ab initio calculations have been performed on OsN and the spectroscopic properties of the low-lying electronic states have been calculated. Our assignments are supported by these calculations. The ground state of OsN has been identified as a 2Δi state consistent with the observations for the isoelectronic IrC molecule [Jansson et al., Chem. Phys. Lett. 4, 188 (1969); J. Mol. Spectrosc. 36, 248 (1970)]. The 1σ22σ21π41δ33σ2 electron configuration has been proposed for the ground state and the configurations for the other low-lying electronic states have also been discussed. This work represents the first experimental or theoretical investigation of the electronic spectra of OsN.