Laser cooling of BeCl and BeBr molecules in an ab initio method

Abstract

In this study, the feasibility of laser-cooling of BeCl and BeBr molecules is studied using ab initio quantum chemistry. The potential energy curves for the X(2)Σ(+), A(2)Π, and 2(2)Π electronic states of BeCl and BeBr are plotted based on multi-reference configuration interaction plus Davidson corrections (MRCI + Q), and the spin-orbit coupling (SOC) effects are considered at the MRCI + Q level. The calculated spectroscopic parameters agree with the experimental data. Highly diagonally distributed Franck-Condon factors are determined for the A(2)Π(ν' = 0) ← X(2)Σ(+)(ν'' = 0) transition: f00(BeCl) = 0.947 and f00(BeBr) = 0.966. Moreover, the suitable radiative lifetimes τ of the A(2)Π(ν' = 0) state are determined for rapid laser cooling: τ(BeCl) = 18.38 ns and τ(BeBr) = 27.09 ns. The proposed cooling wavelengths of both BeCl and BeBr are within the ultraviolet region at λ00(BeCl) = 358.51 nm and λ00(BeBr) = 379.38 nm. Laser cooling schemes for BeCl and BeBr molecules are also developed in consideration of the SOC effects. These results indicate that the inclusion of SOC effects does not affect the judgment of the feasibility of laser cooling of BeCl and BeBr molecules, even for the given BeBr molecules in which the SOC effect is significant.

Two Cycling Centers in One Molecule: Communication by Through-Bond Interactions and Entanglement of the Unpaired Electrons

“…Diagonal FCFs can be realized in molecules in which a single unpaired electron is localized at the cycling center (often, an alkaline-earth metal, a rare-earth metal, or a lanthanide), giving rise to atom-like transitions. Several molecules in this class have been experimentally laser-cooled to (sub)­millikelvin temperatures, − and many more have been proposed on the basis of electronic structure calculations. − Particularly noteworthy are breakthroughs by Doyle’s group, who succeeded in laser-cooling SrOH and, more recently, YbOH, opening possibilities for the cooling of even larger polyatomic molecules with various cycling centers. , The ability to laser-cool polyatomic molecules is crucial for progress in this domain: for example, symmetric-top molecules offer new opportunities in the field of quantum computing and precision measurements …”

Laser cooling of copper monofluoride: a theoretical study including spin–orbit coupling

“…) transition is consistent with the previous theoretical and experimental results, 21,39 and much shorter than those of the A 1 S þ 0 þ (n 0 ¼ 0) / a 3 S + 1 , b 3 P 1,0 + transitions which are rstly predicted here. Compared to the radiative lifetime of the laser cooling transitions for alkali earth metal halides, 17 the value obtained for CuF is a little longer for the 3d-4s orbitals jumping on the Cu + ion. 24 However, it is still a sufficiently short lifetime that could provide a signicant rate (10 5 to 10 8 s À1 ) of optical cycling.…”

“…6 One of the most notable successes was the rst direct laser cooling of SrF to the mK level, 7,8 which initiated more studies on other laser cooling candidates. [9][10][11][12][13][14][15][16][17][18] Very recently, some main group metal hydrides and halides were identied as the promising targets for direct laser cooling theoretically. [13][14][15][16][17][18] However, the study on laser cooling of transition metal diatomics is very limited.…”

“…[9][10][11][12][13][14][15][16][17][18] Very recently, some main group metal hydrides and halides were identied as the promising targets for direct laser cooling theoretically. [13][14][15][16][17][18] However, the study on laser cooling of transition metal diatomics is very limited.…”

Laser cooling of CH molecule: Insights from ab initio study

“…In published research, it was predicted that some alkaline-earth-metal hydrides and halides, such as BeH, MgH, BeCl, could be laser-cooled. [13][14][15][16][17] These molecules have one thing in common: they have no intervening state between the proposed transition for the laser cooling. Therefore, it is necessary to ensure that if an intervening state exists, there is nonetheless closed cycling between the upper state and the ground state of the transition.…”