Browsing by Author "Ding, R."
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Item Creation of Rydberg Polarons in a Bose Gas(American Physical Society, 2018) Camargo, F.; Schmidt, R.; Whalen, J.D.; Ding, R.; Woehl, G. Jr.; Yoshida, S.; Burgdörfer, J.; Dunning, F.B.; Sadeghpour, H.R.; Demler, E.; Killian, T.C.We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a p-wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral line shape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, n. Spectral features are described with a functional determinant approach (FDA) that solves an extended Fröhlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with a FDA.Item Lifetimes of ultra-long-range strontium Rydberg molecules(American Physical Society, 2016) Camargo, F.; Whalen, J.D.; Ding, R.; Sadeghpour, H.R.; Yoshida, S.; Burgdörfer, J.; Dunning, F.B.; Killian, T.C.The lifetimes of the lower-lying vibrational states of ultra-long-range strontium Rydberg molecules comprising one ground-state 5s2 1S0 atom and one Rydberg atom in the 5s38s3S1 state are reported. The molecules are created in an ultracold gas held in an optical dipole trap and their numbers determined using field ionization, the product electrons being detected by a microchannel plate. The measurements show that, in marked contrast to earlier measurements involving rubidium Rydberg molecules, the lifetimes of the low-lying molecular vibrational states are very similar to those of the parent Rydberg atoms. This results because the strong p-wave resonance in low-energy electron-rubidium scattering, which strongly influences the rubidium molecular lifetimes, is not present for strontium. The absence of this resonance offers advantages for experiments involving strontium Rydberg atoms as impurities in quantum gases and for testing of theories of molecular formation and decay.Item Lifetimes of ultralong-range Strontium Rydberg molecules in a dense BEC(IOP, 2017) Camargo, F.; Whalen, J.D.; Ding, R.; Killian, T.C.; Dunning, F.B.; Pérez-Ríos, J.; Yoshida, S.; Burgdörfer, J.The lifetimes and decay channels of ultralong-range strontium Rydberg molecules that contain tens to hundreds of ground-state atoms within the electron orbit are examined by monitoring the time evolution of the Rydberg population using field ionization.Item Lifetimes of ultralong-range strontium Rydberg molecules in a dense Bose-Einstein condensate(American Physical Society, 2017) Whalen, J.D.; Camargo, F.; Ding, R.; Killian, T.C.; Dunning, F.B.; Pérez-Ríos, J.; Yoshida, S.; Burgdörfer, J.The lifetimes and decay channels of ultralong-range Rydberg molecules created in a dense Bose-Einstein condensate are examined by monitoring the time evolution of the Rydberg population using field ionization. Studies of molecules with values of the principal quantum number, n , in the range n = 49 to n = 72 that contain tens to hundreds of ground-state atoms within the Rydberg electron orbit show that their presence leads to marked changes in the field ionization characteristics. The Rydberg molecules have lifetimes of ∼ 1 − 5 μ s , their destruction being attributed to two main processes: formation of Sr 2 + ions through associative ionization and dissociation induced through L -changing collisions. The observed loss rates are consistent with a reaction model that emphasizes the interaction between the Rydberg core ion and its nearest-neighbor ground-state atom. The measured lifetimes place strict limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.Item Lifetimes of ultralong-range strontium Rydberg molecules in cold dense gases(IOP Publishing, 2017) Whalen, J.D.; Camargo, F.; Ding, R.; Killian, T.C.; Dunning, F.B.; Pérez-Ríos, J.; Yoshida, S.; Burgdörfer, J.The lifetimes and decay channels of ultralong-range Rydberg molecules created in a dense Bose-Einstein condensate (BEC) are examined by monitoring the time evolution of the Rydberg population using field ionization. The Rydberg molecules, which contain tens to hundreds of ground state atoms within the electron orbit, have lifetimes of ~ 1 to 5 µs, their destruction being attributed to two main processes: formation of ${{\rm{Sr}}}_{2}^{+}$ ions through associative ionization, and dissociation induced through L-changing reactions. The observed loss rates are consistent with a reaction model that emphasizes the interaction between the Rydberg core ion and its nearest neighbor ground state atom. The application of this model to earlier measurements of strontium dimer lifetimes at lower densities is discussed..Item Photoassociative spectroscopy of a halo molecule in 86Sr(American Physical Society, 2018) Aman, J.A.; Hill, J.C.; Ding, R.; Hazzard, Kaden R.A.; Killian, T.C.; Kon, W.Y.We present two-photon photoassociation to the least-bound vibrational level of the X1Σ+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.Item Spectroscopy of $^{87}\mathrm{Sr}$ triplet Rydberg states(American Physical Society, 2018) Ding, R.; Whalen, J.D.; Kanungo, S.K.; Killian, T.C.; Dunning, F.B.A combined experimental and theoretical spectroscopic study of high-n, 30≲n≲100, triplet S and D Rydberg states in 87Sr is presented. 87Sr has a large nuclear spin I=9/2, and at high-n the hyperfine interaction becomes comparable to, or even larger than, the fine structure and singlet-triplet splittings, which poses a considerable challenge both for precision spectroscopy and for theory. For high-n S states, the hyperfine shifts are evaluated nonperturbatively, taking advantage of earlier spectroscopic data for the I=0 isotope 88Sr, which results in good agreement with the present measurements. For the D states, this procedure is reversed by first extracting from the present 87Sr measurements the energies of the 3D1,2,3 states to be expected for isotopes without hyperfine structure (88Sr), which allows the determination of corrected quantum defects in the high-n limit.Item Theory of excitation of Rydberg polarons in an atomic quantum gas(American Physical Society, 2018) Schmidt, R.; Whalen, J.D.; Ding, R.; Camargo, F.; Woehl, G. Jr.; Yoshida, S.; Burgdörfer, J.; Dunning, F.B.; Demler, E.; Sadeghpour, H.R.; Killian, T.C.We present a quantum many-body description of the excitation spectrum of Rydberg polarons in a Bose gas. The many-body Hamiltonian is solved with a functional determinant approach, and we extend this technique to describe Rydberg polarons of finite mass. Mean-field and classical descriptions of the spectrum are derived as approximations of the many-body theory. The various approaches are applied to experimental observations of polarons created by excitation of Rydberg atoms in a strontium Bose-Einstein condensate.