Triplet-singlet conversion by broadband optical pumping

TL;DR

This paper demonstrates a broadband optical pumping method to convert cold Cs₂ molecules from the triplet state to the singlet ground state, achieving high efficiency and vibrational cooling, with potential applicability to other molecules.

Contribution

The authors introduce a broadband laser technique for triplet-to-singlet conversion in molecules, including a vibrational cooling scheme, advancing molecular state control methods.

Findings

Successful conversion of Cs₂ molecules to the singlet ground state

Implementation of vibrational cooling enhances ground state population

Method is general and applicable to other molecular species

Abstract

We demonstrate the conversion of cold Cs_{2} molecules initially distributed over several vibrational levels of the lowest triplet state a^{3}\Sigma_{u}^{+} into the singlet ground state X^{1}\Sigma_{g}^{+}. This conversion is realized by a broadband laser exciting the molecules to a well-chosen state from which they may decay to the singlet state throug\textcolor{black}{h two sequential single-photon emission steps: Th}e first photon populates levels with mixed triplet-singlet character, making possible a second spontaneous emission down to several vibrational levels of the X^{1}\Sigma_{g}^{+} states. By adding an optical scheme for vibrational cooling, a substantial fraction of molecules are transferred to the ground vibrational level of the singlet state. The efficiency of the conversion process, with and without vibrational cooling, is discussed at the end of the article. The presented conversion is general in scope and could be extended to other molecules.