Laser spectroscopy of molecular LiHe: The 3d 2 Delta p 2 Pi transition

Microsolvation of lithium cation in xenon clusters: An octahedral growth pattern

The structural and energetic proprieties for the Li ⁺ Xe_n (n = 1-18) clusters are investigated using both Basin-Hopping combined with Potential Model description (BH-PM) and DFT methods. A structural transition from tetrahedral (4 coordination) form to octahedral (6 coordination) one is observed for n = 6. Above this size, all structures have an octahedral core. The cubic-face-centered arrangement for xenon atoms is detected for Li ⁺ Xe₁₄. To the best of our knowledge, the Li ⁺ Xe_n (n = 1-18) clusters are studied in the present work for the first time using the DFT theoretical approach. The M062X functional combined with aug-cc-pVDZ (for Li) and def2-TZVP (for Xe) basis sets reproduces accurately the CCSD(T) potential energy curve of Li + Xe system. Atom-Centered Density Matrix Propagation (ADMP) molecular dynamic calculations have been carried. Moreover, we investigate the larger sizes n = 31-35, 44, and 55 for the first time using the BH-PM theoretical approach. The closing of the first and second octahedron shells are proved for the n = 6 and 34 sizes, respectively. The relative stabilities of the Li ⁺ Xe_n molecules are also studied by computing the total energy, the binding energy per atoms for each size n. Then, the second energy difference between the size n and its two near neighbors allows identifying the magic number series. Our present data are analyzed, discussed and compared with the available theoretical and experimental data.

Potential energy curves and spin-orbit coupling of light alkali-heavy rare gas molecules

The potential energy curves of the X, A, and B states of alkali-rare gas diatomic molecules, MKr and MXe, are investigated for M = Li, Na, K. The molecular spin-orbit coefficients a(R)=<(2)Π(½)|Ĥ(SO)|(2)Π(½)> and b(R)=<(2)Π(-½)|Ĥ(SO)|(2)Σ(½)> are calculated as a function the interatomic distance R. We show that a(R) increases and b(R) decreases as R decreases. This effect becomes less and less important as the mass of the alkali increases. A comparison of the rovibrational properties deduced from our calculations with experimental measurements recorded for NaKr and NaXe shows the quality of the calculations.

Laser-Spectroscopic Investigation of Higher Excited Electronic States of the KAr Molecule

Higher excited electronic states of the van der Waals molecule 39KAr have been investigated using a supersonic beam and a two-step excitation. Four hundred seventy Doppler-free lines have been observed in the second step leading to the electronic states 5d2Sigma, 5d2Pi, 5d2Delta, and 7s2Sigma. The spectroscopic parameters of rotation, of spin-orbit splitting, of spin-rotation coupling, and of lambda-type doubling have been determined for altogether 19 vibrational levels of these electronic states. The molecular spin-orbit splitting turns out to be -0.42 cm-1 for 5d2Delta and -0.15 cm-1 for 5d2Pi, which is in fair agreement with the theoretical prediction for a Hund's coupling case a. The vibrational numbering was deduced from theoretical calculations of the interatomic potential. Six vibrational levels have been assigned to the 5d2Delta and the 5d2Sigma state, respectively, allowing a determination of the Dunham coefficients in these two states. For the equilibrium parameters of the 5d2Delta state, we obtain Re = 3.22(15) Å, De = 900(80) cm-1. Copyright 1999 Academic Press.