Precision molecular spectroscopy for ground state transfer of molecular quantum gases

TL;DR

This paper demonstrates high-resolution spectroscopy of Cs_2 molecules, identifying optical transitions that enable efficient two-photon STIRAP transfer into the molecular ground state, advancing ultracold molecule formation techniques.

Contribution

It provides detailed spectroscopic data and confirms the feasibility of coherent ground state transfer of Cs_2 molecules using minimal two-photon processes.

Findings

Identification of optical transitions for ground state transfer

Successful demonstration of STIRAP into the vibrational ground state

Potential for efficient formation of ultracold molecular gases

Abstract

One possibility for the creation of ultracold, high-phase-space-density quantum gases of molecules in the rovibrational ground state relies on first associating weakly-bound molecules from quantum-degenerate atomic gases on a Feshbach resonance and then transfering the molecules via several steps of coherent two-photon stimulated Raman adiabatic passage (STIRAP) into the rovibronic ground state. Here, in ultracold samples of Cs_2 Feshbach molecules produced out of ultracold samples of Cs atoms, we observe several optical transitions to deeply bound rovibrational levels of the excited 0_u^+ molecular potentials with high resolution. At least one of these transitions, although rather weak, allows efficient STIRAP transfer into the deeply bound vibrational level |v=73> of the singlet X ^1Sigma_g^+ ground state potential, as recently demonstrated. From this level, the rovibrational ground state level |v=0, J=0> can be reached with one more transfer step. In total, our results show that coherent ground state transfer for Cs_2 is possible using a maximum of two successive two-photon processes or one single four-photon STIRAP process.