The 4pπ 3Πg–a 3Σu+ system in Ne220 and Ne222

Excitation spectra for the 4pπ 3Πg–a 3Σu+ system in Ne220 and Ne222 have been used to characterize the v=0 through v=3 levels in both electronic states. This is the first time levels with v>1 have been characterized experimentally in either dimer. Rotational analyses lead to Be- and αe-values of 0.5638 cm−1 and −0.9000×10−2 cm−1 and of 0.5113 cm−1 and −0.6651×10−2 cm−1 for the a 3Σu+ states in Ne220 and Ne222, respectively. The Be- and αe-values are, respectively, 0.5716 cm−1 and −0.6429×10−2 cm−1 (20Ne2) and 0.5201 cm−1 and −0.4172×10−2 cm−1 (22Ne2) for the 4pπ 3Πg state. The vibrational parameters ωe, xωe are found to be 556.2, 10.2 cm−1, and 593.2, 7.5 cm−1 for the a 3Σu+ state and 4pπ 3Πg state, respectively, in Ne220 with corresponding values of 529.5, 9.75 cm−1, and 567, 7.5 cm−1 in Ne222. The observed vibrational level differences [ΔG(v+1/2)-values] for the 4pπ 3Πg state are within 0.5% of analogous spacings for the ground electronic state (X 2Σu+) of Ne2+ reported by Kim et al. [Phys. Rev. Lett. 68, 1311 (1992)].