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A theoretical investigation of the feasibility of laser-cooling the 24M g19F molecule is performed using ab initio calculations. The low-lying electronic states are determined by the multireference configuration-interaction (MRCI) method, where the Davidson modification ( + 0 with the Douglas-Kroll-Hess scalar relativistic correction is also taken into account. The calculated spectroscopic constants are in excellent agreement with the available experimental data. The Franck-Condon factors (FCFs), radiative lifetimes, and radiative widths are verified by calculating the potential energy curves and the transition dipole moment of the A 2n (v') -*• X 2S +(v) transition. Our calculation indicates that the A 2Tl(u' = 0) -> X 2S + (v = 0) transition provides highly diagonally distributed FCFs (/oo = 0.917) and a short radiative lifetime (r = 7.96 ns) for the A 2n(v' = 0) state, which is short enough for rapid laser cooling. The required cooling wavelengths are in the ultraviolet region. A comprehensive scheme demonstrates the possibility of laser-cooling MgF. Moreover, the C 2S + state is confirmed to be a Rydberg state at the MRCI level, which is in line with experimental conjecture.The B 2 n and D 2 £ + states are also reported, but they have not been observed to date.

A theoretical investigation on the suitability of laser cooling AlF+ and AlCl+ molecular ions is performed by employing ab initio calculations. Four low-lying electronic states are determined using the multi-reference configuration interaction method plus Davidson correction. The calculated spectroscopic constants are in good agreement with the available theoretical and experimental data. The Franck–Condon factors (FCFs) and radiative lifetimes are verified by calculating the potential energy curves (PECs) and transition dipole moments for the C 2Π (v′) → X 2Σ+ (v), C 2Π (v′) → A 2Π (v) and C 2Π (v′) → B 2Σ+ (v) transitions. Our calculation indicates that the C 2Π (v′) → X 2Σ+ (v) transition is provided with sufficiently diagonally distributed FCFs and the radiative lifetimes for the C 2Π (v′) vibrational state are short enough for rapid laser cooling for both AlF+ and AlCl+ molecular ions. However, our calculation also indicates that the AlF+ radical is not suitable for laser cooling due to the predissociation of the C 2Π state. The calculation and analysis of the electronic states demonstrate the possibility of AlCl+ for laser cooling, and give more insight into the behavior of these four low-lying electronic states for further experimental and theoretical study. Its laser-cooling scheme requires one main pumping laser (λ00 = 268 nm) and three repumping lasers (λ10 = 272 nm, λ21 = 273 nm and λ31 = 278 nm). Moreover, the low mass, short radiative lifetime and small vibrational branching loss ratios to the intervening states make the AlCl+ radical suitable for laser cooling in theory.

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Using ab initio calculations based on density functional theory with PBEsol/PBEsol + U method, the electronic and magnetic properties of undoped MgO are investigated. Calculated results demonstrate that both neutral ðV 0 Mg Þ and singly charged Mg vacancy ðV À Mg Þ can introduce magnetic moment to MgO, and the magnetic moment mainly arises from the spin polarization of the partially occupied 2p orbitals of the nearest O atoms. In combination of group theory and molecular orbital theory, it is found that the magnetic moment is originating from the partially occupied e g À orbital. Results also demonstrate that closed shell Mg vacancy ðV 2ÀMg Þ and all of V 0 O , V þ O and V 2þ O cannot lead to magnetic moment in MgO, but V þ O and V 2þ O will change the insulating behavior into n-type conductivity. In MgO with double Mg vacancies, the defects formation energies suggest that two Mg vacancies prefer the next nearest sites to other configurations. In addition, the magnetic coupling induced by two Mg vacancies is mainly due to the p-p hybridization interaction of O atoms. However, the magnetic moment will be drastically reduced or even completely suppressed within PBEsol + U method, and the total density of states reveal that the system with Mg vacancy displays a p-type conductivity character.