Extensions of the recently introduced “Morse/long-range” (MLR) potential function form allow a straightforward treatment of a molecular state for which the inverse-power long-range potential changes character with internuclear separation. Use of this function in a direct-potential-fit analysis of a combination of new fluorescence data for L7,7i2, L6,6i2, and L6,7i2 with previously reported data for the A(Σ1u+) and X(Σ1g+) states yields accurate, fully analytic potentials for both states, together with the analytic “adiabatic” Born–Oppenheimer breakdown radial correction functions which are responsible for the difference between the interaction potentials and well depths for the different isotopologues. This analysis yields accurate well depths of De=8516.709(±0.004) and 8516.774(±0.004)cm1 and scattering lengths of 18.11(±0.05) and 23.84(±0.05)Å for the ground-states of L7,7i2 and L6,6i2, respectively, as well as improved atomic radiative lifetimes of τ(2p)=27.1018(±0.0014)ns for L7i(2p) and 27.1024(±0.0014)ns for L6i(2p).

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