Dark resonances for ground-state transfer of molecular quantum gases

Abstract

One possible way to produce ultra-cold, high-phase-space-density quantum gases of molecules in the rovibronic ground state is given by molecule association from quantum-degenerate atomic gases on a Feshbach resonance and subsequent coherent optical multi-photon transfer into the rovibronic ground state. In ultra-cold samples of Cs(2) molecules, we observe two-photon dark resonances that connect the intermediate rovibrational level vertical bar v=73,J=2 > with the rovibrational ground state vertical bar v=0,J=0 > of the singlet X (1) I pound (g) (+) ground-state potential. For precise dark resonance spectroscopy we exploit the fact that it is possible to efficiently populate the level vertical bar v=73,J=2 > by two-photon transfer from the dissociation threshold with the stimulated Raman adiabatic passage (STIRAP) technique. We find that at least one of the two-photon resonances is sufficiently strong to allow future implementation of coherent STIRAP transfer of a molecular quantum gas to the rovibrational ground state vertical bar v=0,J=0 >

An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

“…Levels |2 and |4 belong to the coupled ( 15 . We have recently identified suitable transitions linking |1 to |5 , where levels |2 , |3 and |4 were chosen to give balanced transition strengths on the four optical transitions 26,30 . For |3 we choose either |v = 73,J = 2 or |v = 73,J = 0 of the X 1 + g ground state with a binding energy of ∼hc ×1,061 cm −1 .…”

“…Here, we exploit the fact that high phase-space densities can readily be achieved for atoms and that atoms can efficiently be associated on Feshbach resonances to form molecules 7 with minimal loss of phase-space density when an optical lattice is present. Subsequent state transfer to a specific hyperfine sublevel of the rovibronic ground state by means of a stimulated multiphoton process then preserves phase-space 26,30 . R = internuclear distance in units of Bohr radius, a 0 .…”

“…Transfer times are typically 4-10 µs. The simulation yields that the transfer efficiency is at present limited by a combination of laser linewidth, which is about 10 kHz when averaged over 1 s, and imperfect adiabaticity owing to finite available laser power to drive the extremely weak transitions of the 5-level scheme 15,26 . Molecules not transferred to |5 as a result of insufficient phase coherence or limited adiabaticity are excited to either |2 or |4 by one of the lasers and are hence pumped into a multitude of rovibrational levels, which do not couple to the rovibrational ground state.…”

Magnetically Tunable Feshbach Resonances in Ultracold Li-Yb Mixtures

“…Figure 3 shows how the resonance positions and widths for 6 Li 174 Yb and 6 Li 173 Yb vary with the scattering length used to scale the potential. For 7 Li 173 Yb, as for 7 Li 174 Yb, the resonance positions depend quite strongly on the quality of the potential curve. However, the resonance widths for all isotopes depend mainly on the Á ðRÞ functions, obtained here from DFT calculations as described above, and are fairly insensitive to the depth of the potential.…”

Calculation of Radiative Parameters for A1Σ+-X1Σ+ Electronic Transition of the KLi Molecule

“…За последние годы значительно выросло число экспериментальных и теоретических публикаций, связанных с получением гомо-и гетероядерных димеров щелочных металлов в основных и возбужденных электронных состоя-ниях при использовании спектральной методики фотоассоциации холодных атомов [1,2]. Важность этих исследований вызвана изучением динамики столк-новения холодных частиц, проведением химических реакций при низких температурах.…”