Rotational analysis of the LiHg 2(2)Pi(3/2)-X-2 Sigma(+)(1/2) (upsilon '=0<-upsilon ''=0,1,2) vibronic bands

We present a complete analysis of the previously reported LiHg 2(2)Pi(3/2)- X(2)Sigma(+) excitation spectrum [X. Li, P. Pircher, D. Gruber, and L. Wind holz, Chem. Phys. Lett. 263, 463 (1996)]. The v' = 0 - v(n) = 0, 1, 2 vibro nic bands are analyzed and the rotational transitions are identified. The a ssigned rotational transitions are initially fitted on a band-to-band basis . A global fit is performed afterwards for all the known vibronic transitio ns of the LiHg molecules. In the fit the ground state molecular constants a re separated into spin-rotation coupling terms and Dunham-type coefficients . The obtained Dunham coefficients are used to derive the molecular potenti al for the ground electronic state using the inverted perturbation approach (IPA). The equilibrium bond length was found to be 2.9528(6) Angstrom for the LiHg ground state. (C) 1999 Academic Press.