The state of NO–Ne

We investigate the A ∼ 2 Σ + state of NO–Ne by high-level ab initio methods, and by (1 + 1) resonance-enhanced multiphoton ionization spectroscopy (REMPI). Despite being able to obtain high-quality spectra of NO–Ar, NO–Kr and NO–Xe, no spectrum of NO–Ne was observed. It is shown that this state is very weakly bound; and that the overlap between the zero-point vibrational energy level in the X ∼ 2 Π state, and the bound levels of the A ∼ 2 Σ + state is very small: hence the Franck–Condon factors are close to zero. The location of the Ne atom outside the 3s Rydberg orbital is the cause of the observations.