Inverted Vibrational and Rotational Excitation of CN(B 2 Σ + ) Produced through Superexcited Ion-Pair States of MCN (M = Na, K, Rb)

International audienc

Potential energy surfaces of the electronic states of Li2F and Li2F−

International audienceThe potential energy surfaces of the ground and low-lying excited states for the insertion reaction of atomic fluorine (F) and fluoride (F−) into the dilithium (Li2) molecule have been investigated. We have carried out explicitly correlated multi-reference configuration interaction (MRCI-F12) calculations using Dunning’s augmented correlation-consistent basis sets. For the neutral system, the insertion of F into Li2 proceeds via a harpoon-type mechanism on the ground state surface, involving a covalent state and an ionic state which avoid each other at long distance. A detailed analysis of the changes in the dipole moment along the reaction coordinate reveals multiple avoided crossings among the excited states and shows that the charge-transfer processes play a pivotal role for the stabilization of the low-lying electronic states of Li2F. For the anionic system, which is studied for the first time, the insertion of F− is barrierless for many states and there is a gradual charge transfer from F− to Li2 along the reaction path. We also report the optimized parameters and the spectroscopic properties of the five lowest states of the neutral and seven lowest states of the anionic systems, which are strongly stabilized with respect to their respective Li2 + F/F− asymptotes. The observed barrierless insertion mechanisms for both systems make them good candidates for investigation under the ultracold regime

Full-Dimensional Ab Initio Potential Energy Surface and Vibrational Energy Levels of Li2H

International audienceWe built a full-dimensional analytical potential energy surface of the ground electronic state of Li2H from ca. 20,000 ab initio multi-reference configuration interaction calculations, including core–valence correlation effects. The surface is flexible enough to accurately describe the three dissociation channels: Li (2s 2S) + LiH (1Σ+), Li2 (1Σg+) + H (1s 2S) and 2Li (2s 2S) + H (1s 2S). Using a local fit of this surface, we calculated pure (J = 0) vibrational states of Li2H up to the barrier to linearity (ca. 3400 cm−1 above the global minimum) using a vibrational self-consistent field/virtual state configuration interaction method. We found 18 vibrational states below this barrier, with a maximum of 6 quanta in the bending mode, which indicates that Li2H could be spectroscopically observable. Moreover, we show that some of these vibrational states are highly correlated already ca. 1000 cm−1 below the height of the barrier. We hope these calculations can help the assignment of experimental spectra. In addition, the first low-lying excited states of each B1, B2 and A2 symmetry of Li2H were characterized

Experimental studies of collisions of excited Li(4p) atoms with C2H4, C2H6, C3H8 and theoretical interpretation of the Li–C2H4 system

International audienc