Observation of the 71Pig state of Na2 by optical-optical double resonance spectroscopy.

The 71Pig Rydberg state of Na2 correlating with the separated atom limit Na(3s) + Na(5p) has been observed using high-resolution cw optical-optical double resonance spectroscopy. A total of 104 identified rovibrational levels in the range v = 0-12 and 11 </= J </= 44 have been assigned to the 71Pig state. Dunham coefficients were determined, and the Rydberg-Klein-Rees potential curve in the range of R = 2.99-4.66 A was derived for the 71Pig state using the observed quantum levels. The important molecular properties are the potential minimum Te = 36 633.00(23) cm-1 at Re = 3.6313(29) A, omegae = 115.75(13) cm-1, and Be = 0.111 22(17) cm-1. A detailed discussion of this investigation of the 71Pig state is provided.