A DPF data analysis yields accurate analytic potentials for Li2(a3Σu+) and Li2(13Σg+) that incorporate 3-state mixing near the 13Σg+ state asymptote

A combined-isotopologue direct-potential-fit (DPF) analysis of optical and photoassociation spectroscopy data for the a(3)Sigma(+)(u) and 1(3)Sigma(+)(g) states of Li-2 has yielded accurate analytic potential energy functions for both states. The recommended M3LR(5.3)(8.0)(3) potential for the a(3)Sigma(+)(u) state of Li-7.7(2) has a well depth of D-e = 333.758(7) cm(-1) and an equilibrium distance of r(e) = 4.17005(3) angstrom, and the associated scattering lengths are a(SL), = -14.759(9) angstrom for Li-7.7(2) and a(SL) = -1906(50) angstrom for Li-6.6(2). In spite of a gap of more than 5200 cm(-1) (between v(1(3)Sigma(+)(g)) = 7 and v(1(3)Sigma(+)(g)) = 62) for which there are no data, the DPF procedure can readily yield a 1(3)Sigma(+)(g) state potential energy function that accurately represents all of the available data and smoothly bridges this gap. For Li-7.7(2) our recommended M3LR(6.3)(3.6)(9) potential has a well depth of D-e = 7093.44(3) cm(-1), an equilibrium distance of r(e) = 3.06514(9)angstrom, and its long-range tail is defined by the lowest energy eigenvalue of a 3 x 3 matrix which takes into account the 3-state mixing near its asymptote. (C) 2011 Elsevier Inc. All rights reserved.