Laser cooling of the OH− molecular anion in a theoretical investigation

Abstract

The schemes for laser cooling of the OH⁻ anion are proposed using an ab initio method. Scalar relativistic corrections are considered using the Douglas–Kroll Hamilton. Spin–orbit coupling (SOC) effects are taken into account at the MRCI+Q level. SOC effects play important roles in the transition properties of the OH⁻ anion. Transition strengths for the transition of the OH⁻ anion cannot be ignored. Large vibrational branching ratios for the and transitions are determined. Short spontaneous radiative lifetimes for the a³Π₁ and A¹Π₁ states are also predicted for rapid laser cooling. The vibrational branching loss ratio to the intervening states a³Π₀ and a³Π₁ for the transition is small enough to enable the building of a laser cooling project. The three required laser wavelengths for the and transitions are all in the visible region. The results imply the probability of laser cooling of the OH⁻ anion via both a spin-forbidden transition and a three-electronic-level transition.