A reexamination of the Rydberg–Klein–Rees potential of the a 3Σ+u state of Na2

The ∼0.1 Å error in the inner wall of the experimental Rydberg–Klein–Rees (RKR) potential for the Na2 a 3Σ+u state [L. Li, S. F. Rice, and R. W. Field, J. Chem. Phys. 82, 1178 (1985)], detected by Jenč and Brandt using the reduced potential curve (RPC) method [F. Jenč and B. A. Brandt, J. Chem. Phys. 91, 3287 (1989)], was due to neglect of centrifugal distortion effects and not due to a fundamental flaw in the LeRoy–Bernstein near-dissociation expansion (NDE) G(v) and B(v) fitting expressions used to generate it. The NDE expressions, in fact, are preferable to the more traditional Dunham expansions of B(v) and G(v) for the fitting of sparse data sets. We have refined the previously published RKR curve to include centrifugal distortion effects without including additional data. The results are in excellent agreement with theoretical predictions, and are probably accurate to ±0.01 Å up to energies within 5 cm−1 of dissociation. The principal constants are Te+Y00=5848.48(22) cm−1, ωe=24.15(2) cm−1, Be=0.0562(1) cm−1, re=5.011(9) Å, and De=175.76(35) cm−1.