Laser cooling of MgCl and MgBr in theoretical approach

Abstract

Ab initio calculations for three low-lying electronic states (X(2)Σ(+), A(2)Π, and 2(2)Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas-Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f00 for A(2)Π3/2,1/2 (υ' = 0) → X(2)Σ(+) 1/2 (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A(2)Π3/2,1/2 (υ' = 0) states for rapid laser cooling are also obtained. The proposed laser drives A(2)Π3/2 (υ' = 0) → X(2)Σ(+) 1/2 (υ″ = 0) transition by using three wavelengths (main pump laser λ00; two repumping lasers λ10 and λ21). These results indicate the probability of laser cooling MgCl and MgBr molecules.

Electronic Structure with Rovibrational Calculations of the Magnesium Monohalides MgX and Their Cations MgX+ (X = Cl, Br, and I)

“…Our calculated values of the equilibrium bond length R e of the ground state X 2 Σ + are relatively consistent with the theoretical data in the literature where the relative differences are as follows: 0.1% 43 ≤ Δ R e / R e ≤ 1.2%, 40 0.3% 42,44 ≤ Δ R e / R e ≤ 0.9%, 46 and 0.5% 42 ≤ Δ R e / R e ≤ 1.5% 46 for MgCl, MgBr, and MgI, respectively. Also, they are in accordance with the experimental data with average relative differences Δ R e / R e = 0.2% for MgCl and Δ R e / R e = 1.0% for MgBr.…”

Theoretical Study of the Feasibility of Laser Cooling the 24Mg35Cl Molecule Including Hyperfine Structure and Branching Ratios

“…For the X 2 Σ + state, Wan et al found a slightly larger equilibrium distance R e of 2.2025 Å compared to the experimental data. Wan et al did not report their result for the anharmonicity constant ω e χ e for the X 2 Σ + state.…”

“…For the X 2 Σ + state, Wan et al found a slightly larger equilibrium distance R e of 2.2025 Å compared to the experimental data. Wan et al did not report their result for the anharmonicity constant ω e χ e for the X 2 Σ + state. However, our calculations yield a shorter equilibrium distance (2.1940 Å) and a slightly larger anharmonicity constant (2.2378 cm –1 ) for the X 2 Σ + state compared to the observed values (2.1960 Å and 2.1000 cm –1 ).…”

“…For instance, the electronic structures for low-lying states of 24 Mg 35 Cl have been elucidated through the first-order configuration interaction (FOCI) and second-order configuration interaction (SOCI) method by Yarkony et al 26 Then, the rotational spectra for the X 2 Σ + state of the 24 Mg 35 Cl molecule in various isotropic forms and vibrational states were observed in the 130−290 GHz frequency range by Bogey et al 29 Hirao et al 30 Mg 35 Cl and 24 Mg 37 Cl molecules were further studied by highresolution Fourier transform spectroscopy (FTS) by Gutterres et al 31 We exploit 24 Mg 35 Cl for the following reasons: (i) Recently, laser cooling of 24 Mg 35 Cl has been studied theoretically. 20 However, some problems are still not solved well, such as the relevant hyperfine structure (HFS) of 24 Mg 35 Cl, the modulating frequency covering all of the hyperfine energy levels by the proposed sideband frequency distributions. (ii) Cold molecules have found great utility in precision measurements.…”

“…Recently, the molecules had been cooled to below 1 mK by some groups. − As early as 2004, Di Rosa presented a brief survey of candidate molecules for laser cooling. Therefore, theoretically, a large number of polar molecules − have also been investigated for the feasibility of their use in laser cooling. As with atomic systems, a potential laser-cooling candidate molecule should meet certain conditions: (a) highly diagonal Franck–Condon factors (FCFs) that limit the vibrational branching and the number of lasers, (b) the excited state should exhibit a short radiative lifetime for a high photon scattering rate, and (c) the absence of an intermediate electronic state between the ground state and the first excited state or the intermediate state having no effect on the laser cooling cycle.…”