OODR Spectroscopy of Na3and Rotational Analysis of a Vibrationally Excited Level in theÃState

Abstract Using optical–optical double resonance techniques the rotational assignment of the A 2 A 2 – X∼ 2 B 2 system of Na 3 could be extended to transitions involving vibrationally excited levels in the A state. About 30 measured transition frequencies were fitted, using the Hamiltonian of an asymmetric rotor and including spin–rotation interaction. The averaged geometry of the sodium trimer in the vibrationally excited A state was derived from the rotational constants. Vibrational classification of the observed A – X∼ bands from a Jahn–Teller analysis by Dugourd et al. ( J. Chem. Phys. 93, 2322, 1990) is discussed.