Absorption spectrum of the Mg2 molecule

The absorption spectrum of the Mg 2 molecule, which occurs in a furnace containing Mg vapor, has been photographed with a high resolution spectrograph. The rotational structures of the bands have been analyzed and the rotational and vibrational constants of the two states determined. The bands are found to arise from a 1 Σ– 1 Σ transition between a very lightly bonded ground state and a more stable excited state. The R.K.R. potential energy curve of the ground state, which has a dissociation energy of 399 cm −1 , has been determined. The more important constants of the ground state are ω e = 51.12 cm −1 , ω e x e = 1.64 cm −1 , r e = 3.890 Å and those of the upper state are ω e = 190.61 cm −1 , ω e x e = 1.14 cm −1 , r e = 3.082 Å.