Determination of the long‐range potential and dissociation energy of the 1 3Δgstate of Na2

The 1 3Δg state of Na2 has been studied extensively by both filtered fluorescence and ionization detection and analyzed by both Dunham‐type expansion and near‐dissociation expansion (NDE) models in the analysis. Our observations have covered 99.998% of the potential well depth with the outermost Rydberg–Klein–Rees (RKR) turning point at 28.02 A. NDE analysis gives Te=28 032.468 (±0.021) cm−1, De=7162.436 (±0.021) cm−1, and Re=3.463 81 (±0.000 28) A. Significant long‐range behavior in the near dissociation levels has been observed. Fitting of the RKR turning points gives the long‐range coefficients C5=1.388 (±0.031)×106 cm−1 A5 and C6=0.4008 (±0.0046)×108 cm−1 A6. These newly observed results show reasonable agreement with recent theoretical calculations.