| This dissertation describes high-resolution (< 0.005cm -1) sub-Doppler Polarization spectroscopy of the A1Sigma u+ ← X1Sigmag + system of Li2 isotopomers. Precise molecular constants and RKR potential curve are obtained for the A1Sigma u+ and X1Sigmag+ states of 6,6Li2. The result indicates that 6,6Li2 dimer has a noticeable electronic isotope shift, which suggests that the Born-Oppenheimer breakdown (BOB) effects are significant.; The subsequent investigation combined high-resolution polarization data for the A1Sigmau+ ← X 1Sigmag+ band system of 6,7Li 2 and 6,6Li with FTIR data for Lithium isotopomers from Lyon, plus earlier observed transitions for 7,7Li2. Our systematic analysis of 8445 rovibrational transitions yields an improved and internally consistent set of molecular constants for the three Lithium isotopomers. The electronic isotope shift determined for the A1Sigma u+ ← X1Sigmag + system from 7,7Li2 to 6,6Li 2 is 0.131(2) cm-1. The leading BOB correction terms indicate that the lighter isotopomers have shallower potential wells in the X1Sigmag+ and A1Sigma u+ states and longer bond lengths in the A1Sigma u+ states.; Also the electronic isotope shifts for a series of singlet states of the Lithium isotopomers, namely, the A1Sigmau +, B1piu, and 11Delta g states, are calculated and compared with the experimental values. The comparison indicates that the theoretical values roughly agree with the experimental results.; By using three accurate theoretical ionization potentials (1 st, 2nd and 3rd I.P.) of both 6Li and 7Li atoms, we determined the energy levels of the three isotopomers at their equilibrium internuclear distance (R = R e) and at their atomic limits (R = infinity) of the X1Sigma g+ and the A1Sigmau + states relative to infinitely separated electrons and nuclei. The resulting adiabatic corrections for the isotopomers are large (∼300 cm -1). However, the observable Born-Oppenheimer breakdown effects are small (only about 1 part in 105). Nevertheless these effects cannot be ignored for high-resolution spectroscopy. |
