B. Bussery

Long-range molecular states dissociating to the three or four lowest asymptotes for the ten heteronuclear diatomic alkali molecules

Abstract Long-range energy matrix elements have been calculated in the multipolar expansion approximation for all the molecular states dissociating to the three or four lowest asymptotes for the molecules LiNa, LiK, LiRb, LiCs, NaK, NaRb, NaCs, KRb, KCs and RbCs using the semi-empirical perturbative model we proposed recently. Two different assumptions have been investigated: including or excluding the spin-orbit effects within each atom. Full numerical results are presented for NaK and LiCs which have been chosen as examples. For the ten molecules in the non-interacting assumption the long-range coefficients C 6 and C 8 have been found for each state when neglecting atomic spin-orbit effects while the fitted value C * 6 and C * 8 are presented for each state when including atomic spin-orbit effects. When considering the interacting states, those dissociating to n s + n ′s and to n s + 5d(Cs) are seen to be slightly perturbed while the states dissociating to n s + n ′p and to n p + n ′s are significantly perturbed. The wavefunctions for the interacting 3 Σ + , 3 Π, 0 + , 0 − , 1, 2 states for the molecules NaK and LiCs are presented for various internuclear distances.

An intermolecular potential for (O2)2 involving O2(1Δg)

Abstract A theoretical interaction potential for the (O 2 ) 2 dimer involving O 2 ( 1 Δ g ) has been constructed following the methodology previously used to characterize the [O 2 ( 3 Σ g − )] 2 dimer [J. Chem. Phys. 99 (1993) 1230]. Potential energy curves are presented for the dimer states dissociating into O 2 ( 3 Σ g − ) + O 2 ( 1 Δ g ) and O 2 ( 1 Δ g ) + O 2 ( 1 Δ g ). Binding energies and splittings have been evaluated for the neutral states of the dimer in various geometries. Present results are discussed relative to the ground state monomer interactions. Angular distributions and potential wells for the states dissociating into [O 2 ( 1 Δ g )] 2 or O 2 ( 1 Δ g ) + O 2 ( 1 Δ g ) have been found similar to those of the states dissociating into [O 2 ( 3 Σ g − )] 2 .

Semi-empirical determination of the long-range molecular states dissociating to C(3PJ)+O(3PJ′)

Abstract We estimate values for the long-range interaction coefficients C 5 , C 6 and C 8 , and the resulting approximate potential energy curves for molecular states of CO which correspond asymptotically to ground state atoms according to the semi-empirical scheme of Bussery and Aubert-Frecon. Our calculated potential curves are in good qualitative agreement with the recent ab initio computations of Rosenkrantz, Bohr and Konowalow for the quintet states.

Long-range interactions between two identical alkali atoms Li and Na in various electronic states

Abstract Long-range multipolar expansion coefficients Cm, m = 3, 5, 6, 8, have been calculated for the interactions Li(2s) + Li(3s), Li(2p) + Li(2p), Li(2s) + Li(2p), and Na(3s) + Na(4s), Na(3s) + Na(3d), Na(3s) + Na(3p) using a perturbative model we proposed recently. Present values are seen to be in very good agreement with previous theoretical results for the asymptote ns + (n + 1)s.

Potential energy curves and vibration-rotation energies for the two purely long-range bound states 1u and 0g− of the alkali dimers M2 dissociating to M(ns2S12) + M(np2P32) with M = Na, K, Rb, and Cs

Abstract The potential energy curves and the vibration-rotation energies have been calculated in the approximation of the multipolar expansion of the interatomic energy including or not second-order terms for the two purely long-range bound states 1 u and 0 g − of the alkali dimers dissociating to M (ns 2 S 1 2 ) + M (np 2 P 3 2 ) for M = Na, K, Rb, and Cs. Results in good agreement with previous ones are obtained when considering only first-order energy terms, and the influence of the second-order terms is discussed.

Calculated long-range ground and excited molecular states of alkali hydride molecules

Abstract Long-range multipolar expansion coefficients C m , m = 6, 8, 10 and long-range potential energy curves have been calculated for the interaction M( n s) + H(1s) and M( n p) + H(1s), for M is Li, Na, K, Rb, Cs, using a perturbative model we proposed recently. Two different representations of the molecular states corresponding to Hunds case “a” coupling and to a ( J , L ) coupling case, respectively, have been investigated.

Semi-empirical investigation of the angular dependence of the interaction energy between two ground-state oxygen molecules

Abstract An orientation-dependent intermolecular potential for two ground-state O 2 molecules has been determined using a modified Kihara potential function based on molecular charge-distribution contours, observed second virial coefficients and long-range electrostatic quadrupolar and dispersion interactions. Good agreement with experimental predictions and ab initio calculations has been displayed.

Coulomb interaction energy including overlap effects for the ground states of LiNa and Na2

Abstract A recently proposed method to calculate first-order electrostatic as well as second-order induction and dispersion energies including charge-overlap effects for the interaction between two atoms each with one active electron is applied to the systems Li(2s) + Na(3s) and Na(3s) + Na(3s), giving the induction energy for both systems. The variation with R of the relative contribution of the overlapping and non-overlapping configuration space regions is discussed for the largest dispersion and induction terms.