High-resolution vacuum ultraviolet laser spectroscopy of the C 0+u ← X 0+g transition of Xe2

Rotationally resolved (1 + 1'), resonance-enhanced, two-photon ionization spectra of the C 0(u)(+) <-- X 0(g)(+) transition of several isotopomers of Xe-2 have been recorded. Rotational constants have been determined for the v' = 14-26 levels of the C 0(u)(+) Rydberg state and the v'' = 0 and 1 levels of the X 0(g)(+) ground state, and band origins have been determined with an absolute accuracy of 0.015 cm(-1) for the transitions to the v' = 14-26 levels of the C 0(u)(+) state of the Xe-129(2), Xe-129-Xe-132, and Xe-131-Xe-136 isotopomers. The equilibrium internuclear separation of the X 0(g)(+) ground state (R-e = 4.3773(49) Angstrom) was determined from the rotational constants of the v'' = 0 and 1 levels. The analysis of the isotopic shifts of the band origins enabled the confirmation of the absolute numbering of the vibrational levels of the C 0(u)(+) state determined by Lipson et al. (R.H. Lipson, P.E. Larocque, and B.P. Stoicheff. J. Chem. Phys. 82, 4470 (1985)). A semiempirical interaction potential for the X 0(g)(+) ground state was derived in a nonlinear fitting procedure using the present spectroscopic results, the positions of the v'' = 2-9 levels determined by Freeman et al. (D.E. Freeman, K. Yoshino, and Y. Tanaka. J. Chem. Phys. 61, 4880 (1974)) and experimental values for the second virial coefficient. The interaction potential is similar to previous semiempirical potentials but the dissociation energy (D-e = (196.1 +/- 1.1) cm(-1)) differs from the value of 183.1 cm(-1) determined in the latest ab initio calculation (