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Register a new userCharacterization of the lowest excited-state ro-vibrational level of $^{23}$Na$^{87}$Rb
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Starting from an ultracold sample of ground-state $^{23}$Na$^{87}$Rb molecules, we investigate the lowest ro-vibrational level of the $b^3Pi$ state with high resolution laser spectroscopy. This electronic spin-forbidden $X^1Sigma^+ leftrightarrow b^3Pi$ transition features a nearly diagonal Franck-Condon factor and has been proposed useful for probing and manipulating the ultracold molecular gas. We measure the transition strength directly by probing the ac Stark shift induced by near resonance light and determine the total excited-state spontaneous emission rate by observing the loss of molecules. From the extracted branching ratio and the theoretical modeling, we find that the leakage to the continuum of the $a^3Sigma^+$ state plays the dominant role in the total transition linewidth. Based on these results, we show that it is feasible to create optical trapping potentials for maximizing the rotational coherence with laser light tuned to near this transition.
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We present the results of an experimental and theoretical study of the electronically excited $tripletex$ state of $^{87}$Rb$_2$ molecules. The vibrational energies are measured for deeply bound states from the bottom up to $v=15$ using laser spectroscopy of ultracold Rb$_2$ Feshbach molecules. The spectrum of each vibrational state is dominated by a 47,GHz splitting into a $cog$ and $clg$ component caused mainly by a strong second order spin-orbit interaction. Our spectroscopy fully resolves the rotational, hyperfine, and Zeeman structure of the spectrum. We are able to describe to first order this structure using a simplified effective Hamiltonian.
We probe photo-induced loss for chemically stable bosonic $^{23}$Na$^{87}$Rb and $^{23}$Na$^{39}$K molecules in chopped optical dipole traps where the molecules spend a significant time in the dark. We expect the effective two-body decay to be largely suppressed in chopped traps due to the small expected complex lifetimes of about $13mu$s and $6mu$s for $^{23}$Na$^{87}$Rb and $^{23}$Na$^{39}$K respectively. However, instead we do observe near-universal loss even at the lowest chopping frequencies we can probe. Our data thus either suggest a so far unknown loss mechanism or a drastic underestimation of the complex lifetime by at least one to two orders of magnitude.
We measure the binding energies of weakly bound Feshbach molecules formed between Na and Rb atoms in their lowest hyperfine Zeeman levels. We form molecules at the Feshbach resonance near 347.64 G and dissociate them by magnetic field modulation. We use the binding energies to refine the singlet and triplet potential energy curves, using coupled-channel bound-state calculations. We then use coupled-channel scattering calculations on the resulting potentials to produce a high-precision mapping between magnetic field and scattering length. We also observe 10 additional $s$-wave Feshbach resonances for Na and Rb in different combinations of Zeeman sublevels of the $F = 1$ hyperfine states. Some of the resonances show 2-body inelastic decay due to spin exchange. We compare the resonance properties with coupled-channel scattering calculations that full take account of inelastic properties.
Since their first experimental observation, ultralong-range Rydberg molecules consisting of a highly excited Rydberg atom and a ground state atom have attracted the interest in the field of ultracold chemistry. Especially the intriguing properties like size, polarizability and type of binding they inherit from the Rydberg atom are of interest. An open question in the field is the reduced lifetime of the molecules compared to the corresponding atomic Rydberg states. In this letter we present an experimental study on the lifetimes of the ^3Sigma (5s-35s) molecule in its vibrational ground state and in an excited state. We show that the lifetimes depends on the density of ground state atoms and that this can be described in the frame of a classical scattering between the molecules and ground state atoms. We also find that the excited molecular state has an even more reduced lifetime compared to the ground state which can be attributed to an inward penetration of the bound atomic pair due to imperfect quantum reflection that takes place in the special shape of the molecular potential.
In this paper we discuss in detail an experimental scheme to test the universality of free fall (UFF) with a differential $^{87}$Rb / $^{85}$Rb atom interferometer applicable for extended free fall of several seconds in the frame of the STE-QUEST mission. This analysis focuses on suppression of noise and error sources which would limit the accuracy of a violation measurement. We show that the choice of atomic species and the correctly matched parameters of the interferometer sequence are of utmost importance to suppress leading order phase shifts. In conclusion we will show the expected performance of $2$ parts in $10^{15}$ of such an interferometer for a test of the UFF.
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