Ab inito study on the electronic structure and laser cooling of SiH

Abstract

Abstract Potential energy curves (PECs) of six electronic states ( X 2 Π , a 4 Σ - , A 2 Δ , B 2 Σ - , C 2 Σ + , and D 2 Σ + ) are calculated 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. By solving the radical Schrodinger equation, the spectroscopic constants of these states are obtained, which agree well with the experimental results. The SOC effects have little influence on spectroscopic constants. The permanent dipole moments (PDMs) and transition dipole moments (TDMs) of SiH molecule are also calculated with the same method. Highly diagonally distributed Franck-Condon factors (FCFs) are determined for the transitions X 2 Π ↔ A 2 Δ ( f 00 = 0.9858) and X 2 Π ↔ C 2 Σ + ( f 00 = 0.9676). Furthermore, the suitable radiative lifetimes τ of the A 2 Δ and C 2 Σ + states are 3.4625 × 10−7 s and 1.6462 × 10−7 s, which are evaluated for rapid laser cooling. Schemes to laser cooling SiH molecule are designed, and the proposed laser cooling drives for the transition X 2 Π ( ν ″ ) ↔ A 2 Δ ( ν ′ ) and X 2 Π ( ν ″ ) ↔ C 2 Σ + ( ν ′ ) both use three wavelengths. Main pump laser λ 00 for the two transitions are 401.31 and 319.64 nm. These results not only prove the feasibility of laser cooling SiH, but also provide a microkelvin cool temperature for this molecule.