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Photoassociative spectroscopy of a halo molecule in
摘要： We present two-photon photoassociation to the least-bound vibrational level of the X 1Σ+g electronic ground state of the 86Sr2 dimer and measure a binding energy of Eb = ?83.00(7)(20) kHz. Because of the very small binding energy, this is a halo state corresponding to the scattering resonance for two 86Sr atoms at low temperature. The measured binding energy, combined with universal theory for a very weakly bound state on a potential that asymptotes to a van der Waals form, is used to determine an s-wave scattering length a = 810.6(3)(9) a0, which is consistent with, but substantially more accurate than, the previously determined a = 798(12) a0 found from mass scaling and precision spectroscopy of other Sr isotopes. For the intermediate state, we use a bound level on the metastable 1S0-3P1 potential. Large sensitivity of the dimer binding energy to light near resonant with the bound-bound transition to the intermediate state suggests that 86Sr has great promise for manipulating atom interactions optically and probing naturally occurring Efimov states.
关键词： scattering length,binding energy,Efimov states,photoassociation,halo molecule,86Sr
更新于2025-09-23 15:21:01
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The RbSr <sup>2</sup> Σ <sup>+</sup> ground state investigated <i>via</i> spectroscopy of hot and ultracold molecules
摘要： We report on spectroscopic studies of hot and ultracold RbSr molecules, and combine the results in an analysis that allows us to fit a potential energy curve (PEC) for the X(1)2S+ ground state bridging the short-to-long-range domains. The ultracold RbSr molecules are created in a mK sample of Rb and Sr atoms and probed by two-colour photoassociation spectroscopy. The data yield the long-range dispersion coefficients C6 and C8, along with the total number of supported bound levels. The hot RbSr molecules are created in a 1000 K gas mixture of Rb and Sr in a heat-pipe oven and probed by thermoluminescence and laser-induced fluorescence spectroscopy. We compare the hot molecule data with spectra we simulated using previously published PECs determined by three different ab initio theoretical methods. We identify several band heads corresponding to radiative decay from the B(2)2S+ state to the deepest bound levels of X(1)2S+. We determine a mass-scaled high-precision model for X(1)2S+ by fitting all data using a single fit procedure. The corresponding PEC is consistent with all data, thus spanning short-to-long internuclear distances and bridging an energy gap of about 75% of the potential well depth, still uncharted by any experiment. We benchmark previous ab initio PECs against our results, and give the PEC fit parameters for both X(1)2S+ and B(2)2S+ states. As first outcomes of our analysis, we calculate the s-wave scattering properties for all stable isotopic combinations and corroborate the locations of Fano–Feshbach resonances between alkali Rb and closed-shell Sr atoms recently observed [V. Barbé et al., Nat. Phys., 2018, 14, 881]. These results and more generally our strategy should greatly contribute to the generation of ultracold alkali–alkaline-earth dimers, whose applications range from quantum simulation to state-controlled quantum chemistry.
关键词： spectroscopy,laser-induced fluorescence,thermoluminescence,ultracold molecules,photoassociation,potential energy curve,Fano-Feshbach resonances,RbSr molecules
更新于2025-09-19 17:15:36