A new pair of singlet-triplet A(1)Sigma (-)(u) similar to b(3)Pi (u) mixed levels of (LiLi)-Li-6-Li-7 has been identified and used here as window levels in pulsed perturbation-facilitated optical-optical double resonance (PFOODR) experiments to study the high-lying triplet 2(3)Delta (g) state. The ne mixed le els reported here enhance access to the high-lying triplet states through the expansion of the Franck-Condon overlap factor range. at the same time allowing for more reliable determination of rotational constants, New molecular constants of the 2(3)Delta (g) state are reported here. (C) 2001 Elsevier Science B.V. All rights reserved.