Observation of the 5p 1Πu Rydberg state of 7Li2

Some weak, collisionally induced transitions in 7 Li 2 have been recorded by Fourier transform spectrometry in the near infrared, following excitation of the 5 d 1 Π g state by optical–optical double resonance. They have been assigned as transitions to the 1 1 Δ g state from levels v =0 and 1 of a new ungerade Rydberg state, 5 p 1 Π u . Quantum defect considerations indicate that the principal quantum number for this new state is 5, and that the assignment to 5 p is compatible with a Rydberg series of which the lowest members would be the B 1 Π u and C 1 Π u states.