Optical Pumping of SiO⁺: How an Intervening Electronic State aids in Ground Rotational State Preparation

State preparation of molecules is a crucial first step in experiments of metrology, fundamental physics, and quantum information. Recently, control over the quantum states of SiO⁺ has been demonstrated^1,2. With an X, A, and B electronic state structure, spectral filtering of light that cycles population between the X and B states can lead to ground or excited rotational state preparation. Here, we present our results modeling the state population dynamics involved. Our results indicate that the electronic A state aids in this process by acting as a pathway for parity flipping. By simulating the rotational population as a function of time, we fit the rates at which rotational state parity is changed and match this to the experiment¹. We find the B-A branching is likely stronger than predicted and in fact beneficial when optical pumping to the ground rotational state. Relevant timescales of other processes that affect state population are modeled and shown, providing a near complete description of optical pumping in SiO⁺.

[1] Stollenwerk, P. R. et al, PRL 125, 113201 (2020)

[2] Antonov, I.O. et al, Nat. Commun. 12, 2201 (2021)