Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-diatom C_8 coefficients. The resulting expressions are applied to dispersion coefficients for Li + Li_2 (triplet) and recommendations are made for the best way to obtain global triatomic potentials that dissociate correctly both to three separated atoms and to an atom and a diatomic molecule.Comment: To be published in a special issue of Molecular Physics in honour of Mark Chil

Photoassociation of a cold atom-molecule pair: long-range quadrupole-quadrupole interactions

The general formalism of the multipolar expansion of electrostatic interactions is applied to the calculation the potential energy between an excited atom (without fine structure) and a ground state diatomic molecule at large separations. Both partners exhibit a permanent quadrupole moment, so that their mutual quadrupole-quadrupole long-range interaction is attractive enough to bind trimers. Numerical results are given for an excited Cs(6P) atom and a ground state Cs2 molecule. The prospects for achieving photoassociation of a cold atom/dimer pair is thus discussed and found promising. The formalism can be easily generalized to the long-range interaction between molecules to investigate the formation of cold tetramers.Comment: 5 figure

Ab initio Cl calculation of dynamic polarizabilities and hyperpolarizabilities of CF

The electric dipole moment of CF+ has been calculated using a large basis set of 118 contracted Gaussian-Type orbitals. We firstly compare our SCF(Self Consistent Field) results obtained by the CPHF (Coupled Perturbed Hartree-Fock) method [1] with previous values [2]. Secondly we report more accurate values obtained by the TDGI (Time Dependent Gauge Invariant) method. New dynamic polarizability and hyperpolarizability are presented at the SCF and correlated level

Ab initio calculation of excited state dipole polarizability -Application to the first

Firstly, imaginary frequency-dependent dipole polarizabilities of Li in its $^2{\rm S}$ ground state and the first $^2{\rm P}$ excited state are calculated from a time-dependent gauge-invariant method using effective core pseudo-potentials and the multi-configuration one-electron wave function. C6 dispersion coefficients of the 2s+2s and 2s+2p dissociations are deduced and also compared with all-electron values. Then, static polarizabilities of Li2 in its ground and first excited $^{1,3}\Sigma_{g,u}^+$ states are obtained at interatomic distance corresponding to the energy minimum of each state

Performance of a gauge-invariant method on calculated dynamic polarizabilities

cited By 39International audienceIn the calculation of the dynamic polarizability including electronic correlation and ensuring gauge invariance, contributions of spectroscopic states and quasispectral series are analyzed. An improvement of our original electric-field variant ket approach is proposed and illustrated by application to H and LiH systems. © 1992 The American Physical Society

Ab initio Cl determination of electric moments and frequency dependent polarizabilities and hyperpolarizabilities for CO

Frequency-dependent electric dipole polarizabilities of CO were computed using a time-dependent gauge invariant (TDGI) method, accounting for a large part of the correlation effects in response properties. The results compare well with both experimental and other theoretical calculations. Reported results also include the Ce dispersion coefficients and the first frequency dependent hyperpolarizability

Choix de la jauge dans le calcul quantique de propriétés électromagnétiques des molécules

Le calcul quantique de propriétés électroniques comme les susceptibilités électriques ou magnétiques nécessite de définir une jauge pour décrire le champ électromagnétique. Dans les ”conditions habituelles” de calcul, les résultats sont dépendants de jauge et le choix de celle-ci devient important. Ce problème est bien connu dans le cas du calcul des susceptibilités magnétiques [1-9], mais peut-être moins dans le cas du calcul des polarisabilités. Nous montrerons l’effet d’un changement de jauge sur le calcul des polarisabilités dynamiques de l’atome d’hydrogène

Dynamic polarizabilities and Van der Waals coefficients for alkali atoms Li, Na and alkali dimer molecules Li

The present paper gives an account of investigations of the polarizability of the alkali atoms Li, Na, diatomics homonuclear and heteronuclear Li2, Na2 and NaLi at SCF (Self Consistent Field) level of approximation and at correlated level, using a time Time-Dependent Gauge Invariant method (TDGI). Our static polarizability values agree with the best experimental and theoretical determinations. The Van der Waals C6 coefficients for the atom-atom, atom-dimer and dimer-dimer interactions have been evaluated

Dynamic polarizabilities and Van der Waals coefficients for the ground 2 2S and excited 2 4Po states of Li

cited By 29International audienceThe dynamic dipole polarizabilities at real and imaginary frequencies have been determined for the ground 2 2S and excited 2 4Po states of Li using our time-dependent gauge-invariant method. Accurate C6 dispersion energy coefficients for the Li(2 2S)-H2 and Li(2 Po4)-H2 systems and their dependence on the intramolecular H-H distance are reported. © 1994 The American Physical Society

Dynamic scalar and tensor polarizabilities for the low-lying 21P0 and 23P0 states of Be

cited By 6International audienceStatic and dynamic scalar α0(ω) and tensor Δα(ω) dipole polarizabilities at real frequencies have been calculated for the two first excited states 2 1P0 and 2 3P0 of Be using the time-dependent gauge-invariant method (TDGI). The results are compared with the previous accurate theoretical data obtained by Themelis and Nicolaides at the static level. The dynamic results proposed here are new and complete our results published previously concerning the 31S and 33S states. In all cases dynamic components are calculated for dipole polarizability up to the first resonances ((latin small letter h with stroke sign) ω = E21P0-21S and (Latin small letter h with stroke sign) ω = E23P0-1D) and ((Latin small leter h with stroke sign) ω = E23P0-3S and (Latin small letter h with stroke sign) ω = E23Po-3D) for the singlet and the triplet states, respectively