One-electron pseudopotential calculations of excited states of LiAr, NaAr, and KAr

Abstract

Ab initio many-electron study for the low-lying states of the alkali hydride cations in the adiabatic representation Theoretical calculation of the excited states of the KCs molecule including the spin-orbit interactionThe potential curves and spectroscopic constants of the excited states of alkali-argon diatomics MRg ͑MϭLi, Na and K, RgϭAr͒ are calculated using usual semilocal single valence electron pseudopotentials on alkali atoms ͓͑M ϩ ͔-core pseudopotentials͒, semilocal pseudopotentials replacing all the electrons of argon ͓͑Ar͔-core pseudopotentials͒, and core polarization pseudopotentials on both centers. All states dissociating into Li͑2s, 2p, 3s, 3p, 3d, 4s, and 4p͒, Na͑3s, 3p, 3d, 4s, 4p, 4d, 5p͒ and K͑4s, 4p, 5s, 3d, 5p, 4d, 6s, 4f , 6p, 5d, 7s, 5f ͒ are considered. The core-core interactions for Li ϩ Ar and Na ϩ Ar are included using the accurate ab initio potentials of Ahmadi et al. ͓G. R. Ahmadi, J. Almlöf, and I. Roeggen, Chem. Phys. 199, 33 ͑1995͒; G. R. Ahmadi and I. Roeggen, J. Phys. B 27, 5603 ͑1994͔͒ while the K ϩ Ar ion data are determined by MP2 all-electron calculations.

One-Electron Pseudo-Potential Determination of Stable Isomers of the Li*Ar n Excited Clusters: Absorption Spectra

“…This hybrid Hamiltonian has been shown to yield accuracy comparable to or even better than that of the existing Benchmark calculations for free diatomics LiAr, NaAr and KAr [1] where the comparison with the high resolution spectroscopic data can be made. Using such pseudopotential techniques, we restrict the number of the active electrons to one for the whole system.The computational cost is strongly reduced and it becomes possible to implement the electronic structure calculation with global optimization methods in order to explore the potential energy surfaces (PES's) and find the geometry of the lowest energy isomers of Li*Ar n polyatomic exciplexes.…”

“…The atomic transitions and oscillator strengths are compared in Table 1 with the data (Moore [39] and Gaupp [40]). As in previous studies of alkali-rare gas clusters [1,7,20], we added a 5s 4p Gaussian basis set on each argon atom in order to allow for the orbital deformation in their vicinity. To know how the spectrum of the Lithium atom changes when it is implanted into the argon cluster, we calculate the optical vertical spectrum of LiAr n clusters with the same basis used for free lithium atom.…”

“…The argon was treated as a zero-electron atom with all its electrons in the core via an atomic [Ar] core pseudopotential determined by Duplaa and Spiegelman [35]. The Ar pseudopotential is used in the investigation of the absorption spectroscopy of atoms or molecules interacting with argon clusters or matrices [1,7,20], and [36]. The pseudopotentials also incorporate core polarization operators (so-called core-polarization potentials CPPs) using the ldependent formulation of Foucrault and coworkers [37] generalizing the initial formulation proposed by Müller and Meyer [38].…”

“…The single valence electron pseudopotential for the [Li ? ] core has been widely used in accurate standard valence calculations [1]. The argon was treated as a zero-electron atom with all its electrons in the core via an atomic [Ar] core pseudopotential determined by Duplaa and Spiegelman [35].…”

“…In particular, for a sufficiently high excitation energy, one expects the occurrence of cluster states with Rydberg character corresponding to the picture of an excited electron surrounding an ionic cluster core, as shown in the works of Fujisaki [18,19] for K (5s)Xe n clusters. The convergence of Rydberg series towards the parent ions is well known in atoms, diatomics, and small molecules [1,20]. Boyle et al [21] have recently observed Rydberg series in C 60 .…”