A theoretical study on laser cooling of silicon monofluoride

The feasibility of direct laser cooling of silicon monofluoride (SiF) is investigated and assessed using the internally contracted multireference configuration interaction method with the Davidson correction and entirely uncontracted aug-cc-pwCV5Z basis sets. As for the A2Σ+(ν′=0)→X2Π transition, the computed radiative lifetime is 0.69 μs and the vibrational branching ratio Rν′ν is highly diagonally distributed with the R00 being 0.994, which are desirable for rapid and efficient laser cooling. In addition, good agreement is achieved between our computed spectroscopic properties and the available experimental data for the X2Π and A2Σ+ states of SiF. We propose a kind of laser cooling scheme, in which the wavelengths are located in the visible region. Both our calculated Doppler and recoil temperatures are of the order of μK, and the calculated minimum distance necessary to bring the velocity of a SiF beam to that suitable for trapping is 13 cm, indicating that the SiF molecule can be cooled to the ultracold regime through the proposed scheme.

Proposed laser cooling scheme for SiF using the A2Σ+←X2Π transitions. Solid arrows indicate laser-driven transitions at certain wavelengths λν′,ν. Dashed arrows indicate spontaneous decays from the A2Σ+(ν′=0,1) state with the calculated Rν′ν. 130