Gerade/ungerade symmetry- breaking in HD at the n =2 dissociation limit
We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of 1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w
Lithium Hydrides and Lithium Dimers: Sub‐Doppler Spectroscopy and Dynamics
Deep insights into molecular structures and dynamics were obtained for lithium dimers and lithium hydrides by sub-Doppler spectroscopy combining molecular beams and cw tunable laser beams. For 7Li7Li species, accurate spectroscopic studies of the B 1Πu-X 1Σg+ system were carried out, with the measurement of hundreds of wave numbers and with the determination of dissociation rates due to tunneling through the potential barrier of the B 1πu state. They led to the full description of the B state potential, including its barrier. For 6Li7Li species, weak but non-negligible dissociation rates in the B 1Πu state were observed, measured and interpreted assuming that an electronic coupling between the B 1Πu and 1 1Πg states takes place through an ungerade-gerade symmetry breaking. For LiH species, the A 1Σ+-X 1 Σ+ system was revisited for both isotopomers. For this molecule, dynamical effects are predicted in highly-excited Rydberg states, that could be studied by use of similar sub-Doppler techniques.
Perturbed structure of molecular hydrogen near the second dissociation limit.
The region of the second dissociation limit of H{sub 2} converging to H(1{ital s})+H(2{ital s},2{ital p}) has been investigated using high-resolution double-resonance spectroscopy through the {ital E},{ital F} {sup 1}{Sigma}{sub {ital g}}{sup +} state. Transitions to the very high vibrational levels of the {ital B} {sup 1}{Sigma}{sub {ital u}}{sup +}, {ital B}{prime} {sup 1}{Sigma}{sub {ital u}}{sup +}, and {ital C} {sup 1}{Pi}{sub {ital u}} states have been measured with 0.02-cm{sup {minus}1} accuracy. Numerous perturbations and unexpected transitions are observed as far as 10 cm{sup {minus}1} below the dissociation limit. This complex structure, still not fully understood, arises from a combination of electronic, fine-structure, and hyperfine interactions.