Cold interactions and chemical reactions of linear polyatomic anions with alkali-metal and alkaline-earth-metal atoms

Abstract

We consider collisional studies of linear polyatomic ions immersed in ultracold atomic gases and investigate the intermolecular interactions and chemical reactions of several molecular anions (OH − , CN − , NCO − , C2H − , C4H − ) with alkali-metal (Li, Na, K, Rb, Cs) and alkaline-earth-metal (Mg, Ca, Sr, Ba) atoms. State-of-the-art ab initio techniques are applied to compute the potential energy surfaces (PESs) for these systems. The coupled cluster method restricted to single, double, and noniterative triple excitations, CCSD(T), is employed and the scalar relativistic effects in heavier metal atoms are modeled within the small-core energy-consistent pseudopotentials. The leading long-range isotropic and anisotropic induction and dispersion interaction coefficients are obtained within the perturbation theory. The PESs are characterized in detail and their universal similarities typical for systems dominated by the induction interaction are discussed. The two-dimensional PESs are provided for selected systems and can be employed in scattering calculations. The possible channels of chemical reactions and their control are analyzed based on the energetics of reactants. The present study of the electronic structure is the first step towards the evaluation of prospects for sympathetic cooling and controlled chemistry of linear polyatomic ions with ultracold atoms.

Cold reactive and nonreactive collisions of Li and Rb with C2− : Implications for hybrid-trap experiments

“…However, correlating the core orbitals of C − 2 was necessary to achieve convergence and avoid root flipping problems in the repulsive region of the PES. 22 , but smaller than for Rb-OH − for which the interaction energy at the minimum is about 2 eV 52 . The well depth of LiC − 2 is about 1.7 times larger than for RbC − 2 , in agreement with the trend observed for several other systems where Li compounds are found to be more strongly bound 22,24 .…”

“…Several such candidates have been recently proposed for sympathetic cooling with ultracold alkali and alkaline earth atoms 22 . However, the position of the AD region will still depend on the atomic collision partner.…”

Interactions and chemical reactions in ionic alkali-metal and alkaline-earth-metal diatomic AB+ and triatomic A2B+ systems

“…In order to obtain potential energy curves (PECs) and surfaces (PESs) within the Born-Oppenheimer approximation, we adopt the computational scheme successfully applied to the ground-state interactions between polar alkali-metal dimer [56] and between linear polyatomic anions with alkali-metal and alkaline-earth-metal atoms [43]. Thus, to calculate PECs and PESs we employ the close-shell or spin-restricted open-shell coupled cluster methods restricted to single, double, and noniterative triple excitations, starting from the restricted close-shell or open-shell Hartree-Fock orbitals, CCSD(T) [68,69].…”

Interactions of benzene, naphthalene, and azulene with alkali-metal and alkaline-earth-metal atoms for ultracold studies

“…In order to investigate intermolecular interactions, we adopt the computational scheme successfully applied to the ground-state interactions between polar alkali-metal dimer 75 and polyatomic molecular ions with alkali-metal and alkaline-earth-metal atoms 76 . Thus, to calculate PESs for molecules interacting with alkaline-earth-metal atoms (alkali-metal atoms) we employ the closed-shell (spin-restricted open-shell) coupled cluster method restricted to single, double, and noniterative triple excitations, starting from the restricted closed-shell (openshell) Hartree-Fock orbitals, CCSD(T) 77,78 .…”