For nearly all states dissociating below the ionic limit, we perform an adiabatic and diabatic study for 1Σ+ and 3Σ+ electronic states dissociating into Cs (6s, 6p, 5d, 7s, 7p, 6d, 8s and 4f) + H (1s). Furthermore, we present the adiabatic results for the 1–5 1,3Π and 1–3 1,3Δ states. The calculations rely on an ab initio pseudopotential, semi-empirical operator core-valence correlation and full valence CI approaches, combined to an efficient diabatization procedure. For the low-lying states, our spectroscopic constants and vibrational level spacing are in very good agreement with the available experimental data. Diabatic potentials and dipole moments are analysed, revealing the strong imprint of the ionic state in the 1Σ+ adiabatic states. The H electron affinity correction was accounted for by the use of the efficient diabatization method. This leads to a better agreement with the available experimental data. Experimental suggestions are also given for the higher excited states based on their unusual behaviour.

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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.

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The BeCs+ system represents a possible future candidate for the realization of samples of cold or ultra-cold molecular ion species that it has been not yet investigated experimentally nor theoretically....

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