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.
We systematically investigate the structural, electronic, and magnetic properties of a new pentagonal CoBiS monolayer using first-principles and Monte Carlo simulations. We find that Penta-CoBiS is stable mechanically, dynamically, and thermally and is an antiferromagnetic semiconductor with an indirect band gap of 0.5 eV with HSE functional. In addition, the band-gap increased by applying in-plane biaxial strain. We further show that this monolayer has an in-plane easy axis and possesses large intrinsic Dzyaloshinskii–Moriya interaction because of the broken inversion symmetry, and strong spin–orbit coupling originated from the Bi atoms. Moreover, the Néel temperature is also predicted using Monte Carlo simulations. An out-of-plane magnetic field B is then applied to compensate the in-plane anisotropy. It is found that for B = 1.72 T the spins are fully polarized to the out-of-plane direction. Our results demonstrate that Penta-CoBiS monolayer may find numerous applications in flexible spintronics and electronics.
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