The 3 1Σ+g ‘‘shelf’’ state of Na2.

The 3 1Σ+g state of Na2 has been extensively studied using an optical–optical double resonance technique and a shielded cylindrical space-charge-limited ionization detector. A wide range of vibrational quantum numbers 0≤v≤141 was observed which covered over 99.9% of the potential well depth. A ‘‘shelf’’ on the potential energy curve was found near v=23. A hybrid potential was constructed based on the Rydberg–Klein–Rees (RKR) potential curve and a local inverse perturbation approach (IPA) for the shelf region. For this potential, there is a shallow second local minimum ∼5 cm-1 in depth at the shelf region. The long range energy also compares well with long range theory. [ABSTRACT FROM AUTHOR]