The outer well of the NaH C-1 Sigma(+) excited state was determined using pulsed optical-optical double resonance fluorescence depletion spectroscopy. The level-selected fluorescence of the A(1)Sigma(+) state is depleted back to the ground state when a probe laser excites the molecules to the C-1 Sigma(+) state. A total of 456 rovibrational levels, v = 5-33 and J = 1-11, were observed. A set of Dunham constants and the Rydberg-Klein- Rees (RKR) potential curve for the outer well were reported. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.