Rovibrational cooling of molecules by optical pumping

TL;DR

This paper demonstrates a simple optical pumping method to efficiently cool cesium dimers to their rovibrational ground state, enabling potential applications in molecular laser cooling and quantum control.

Contribution

The authors introduce a novel optical pumping technique that achieves rovibrational cooling of molecules with high efficiency, applicable to various molecular species.

Findings

Achieved up to 40% efficiency in cooling Cs2 molecules to the ground state.

Demonstrated the method's simplicity and potential for extension to other molecules.

Opened new perspectives for laser cooling of molecular external degrees of freedom.

Abstract

We demonstrate rotational and vibrational cooling of cesium dimers by optical pumping techniques. We use two laser sources exciting all the populated rovibrational states, except a target state that thus behaves like a dark state where molecules pile up thanks to absorption-spontaneous emission cycles. We are able to accumulate photoassociated cold Cs2 molecules in their absolute ground state (v = 0, J = 0) with up to 40% efficiency. Given its simplicity, the method could be extended to other molecules and molecular beams. It also opens up general perspectives in laser cooling the external degrees of freedom of molecules.