On the Band Spectrum of HfO

The band spectrum of the diatomic molecule Hf 180 O 16 has been investigated in emission in the region 2 300-11 500 Å. 28 bands belonging to 6 different band systems have been rotationally analysed. The 6 band systems are due to transitions from 6 excited electronic states to the ground state X 1 Σ. Perturbations between two excited 1 Π states have been observed. Results are also given for three transitions not involving the ground state. Molecular constants in cm -1 for the ground state X 1 Σ of Hf 180 O 16 : ω e = 974.09 (3) ω e χ e = 3.228 (6) B e = 0.386537 (7) α e = 0.001724 (3) D e = 0.2438 (3) × 10 -6 β e = 0.6 (2) × 10 -9 The figures in brackets are the error limits referred to the last preceeding figure.