Core-Penetrating Rydberg Series of BaF: New Electronic States in then* ≈ 4 Region

We report results of our studies of the electronic spectrum of the BaF molecule in the energy region of T 0 = 31 460–32 400 cm −1 (3.88 n * −1 ): K 2 Π 1/2 ( T 0 = 31 996), 4.08 2 Σ + ( T 0 = 32 166.293(2), B 0 = 0.2333892(17)), 3.94 2 Δ ( T 1 = 32 252.426(2), B 1 = 0.2294684(16), A 1 = 0.879(13)), and J 2 Π ( T 0 = 32 297.918(2), B 0 = 0.22952165(51), A 0 = 57.196(1)). In addition, the previously observed G 2 Σ + ( T 0 = 30 969.715(2), B 0 = 0.2297411(13)) and H 2 Σ + ( T 0 = 31 606.238(2), B 0 = 0.23031573(85)) states were rotationally analyzed for the first time. We verified by isotope analysis that the G 2 Σ + state, previously reported by J. Singh and H. Mohan [ Indian J. Pure Appl. Phys. 11, 918–922 (1973)], had been incorrectly assigned vibrationally. The I 2 Σ + state, which Singh and Mohan observed at low resolution, was absent from our spectra and we suspect that this state belongs to a species other than BaF. Electronic term values for the remaining seven not yet observed BaF core-penetrating Rydberg states below n * = 6 were predicted by interpolation of well-characterized Rydberg series. We suggest that the E ″ state, assigned by Effantin et al. as a 2 Π 1/2 state [C. Effantin, A. Bernard, J. D'Incan, E. Andrianavalona, and R. F. Barrow, J. Mol. Spectrosc. 145, 456–457 (1991)] must be reassigned as a 2 Δ state.