“…Furthermore, the electronic spectrum of the LuF molecule has been recorded experimentally using a hollow cathode lamp by D’Incan et al 18 and Effantin et al 19 ; they assigned the following notation for the excited states : A 1 Σ + , B 1 Π, D 1 Π, E 1 Π, and F 1 Σ + . However, similarly to Assaf et al 29 and Hamadeh et al 27 , in our work, the first excited state was found to be a 1 Π state, with a transition energy T e = 24 973 cm −1 . This state doesn’t correspond to the observed A, B, or D systems, but to the reported E 1 Π state, where the spectroscopic constants average relative differences with our calculations are 2.0% for Te, 1.5% for Re, 0.3% for ω e and 2.7% for Be.…”