The r = 2-21 levels of the Na-2 6(3)Sigma(g)(+) state have been observed by perturbation facilitated optical-optical double resonance (PFOODR) spectroscopy. The vibrational numbering is confirmed by simulation of the 6(3)Sigma(g)(+) --> a(3)Sigma(u)(+) bound-free transition. Molecular constants and RKR potential curve of the 6(3)Sigma(g)(+) state are reported. Perturbations of the 6(3)Sigma(g)(+)state are discussed. (C) 2004 Elsevier Inc. All rights reserved.