Abstract
Experiments with cold ion–atom mixtures have recently opened the way for the production and application of ultracold molecular ions. Here, in a comparative study, we theoretically investigate ground and several excited electronic states and prospects for the formation of molecular ions composed of a calcium ion and an alkali-metal atom: CaAlk+ (Alk = Li, Na, K, Rb, Cs). We use a quantum chemistry approach based on non-empirical pseudopotentials, operatorial core-valence correlation, large Gaussian basis sets, and full configuration interaction method for valence electrons. Adiabatic potential energy curves, spectroscopic constants, and transition and permanent electric dipole moments are determined and analyzed for the ground and excited electronic states. We examine the prospects for ion-neutral reactive processes and the production of molecular ions via spontaneous radiative association and laser-induced photoassociation. After that, spontaneous and stimulated blackbody radiation transition rates are calculated and used to obtain radiative lifetimes of vibrational states of the ground and first-excited electronic states. The present results pave the way for the formation and spectroscopy of calcium–alkali-metal-atom molecular ions in modern experiments with cold ion–atom mixtures.
Highlights
Cold mixtures of alkaline-earth-metal ions and alkalimetal atoms have recently emerged as a new field of research at the crossroad of quantum physics and chemistry [1,2,3]
Motivated by recent experimental studies on ultracold mixtures of Ca+ ions immerse in alkali-metal atoms, in a comparative study, we have investigated the electronic structure and the prospects for the formation of the molecular ions composed of a calcium ion and an alkali-metal atom: CaAlk+ (Alk=Li, Na, K, Rb, Cs)
The electronic structure data have been employed to examine the prospects for the ion-neutral reactive processes and production of molecular ions via spontaneous radiative association and laser-induced photoassociation
Summary
Cold mixtures of alkaline-earth-metal ions and alkalimetal atoms have recently emerged as a new field of research at the crossroad of quantum physics and chemistry [1,2,3]. A new apparatus with a mixture of laser-cooled Ca+ ions in a linear Paul trap overlapped with ultracold K atoms in a magneto-optical trap was presented [28]. This setup incorporates a high-resolution time-of-flight mass spectrometer designed for radial extraction and detection of reaction products opening the way for detailed studies of the state-selected formation of CaK+ molecular ions.
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