Rotational cooling of heteronuclear molecular ions with¹Σ, ²Σ, ³Σ, and²II electronic ground states

A cooling schemes for rotational cooling of translational cold molecular ions in the ¹σ, ²σ, ³σ and ²π electronic ground states were presented. The schemes for the rare ³σ electronic state, can be realized by optical pumping with a pulsed laser beam by combining the inclusion of a broadband incoherent source. The translational motion of molecular ions can be effectively cooled to translational temperatures below 100 mK in ion traps through Coulomb interactions with laser-cooled atomic ions. The results show that the schemes relied on one or two laser-driven transitions with the possible inclusion of a tailored incoherent far-infrared radiation field.