Browsing by Author "Yoshida, S."
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Item Autoionization of very-high-n strontium Rydberg atoms(IOP Publishing, 2017) Zhang, X.; Fields, G.; Dunning, F.B.; Yoshida, S.; Burgdörfer, J.The autoionization of high n, n~280-430, strontium Rydberg states through excitation of the 5s 2S1/2→5p 2P1/2 transition in the core ion is investigated. The autoionization rates decrease rapidly as L is increased paving the way for production of long-lived two-electron-excited planetary atoms.Item Autoionization of very-high-n strontium Rydberg states(American Physical Society, 2018) Fields, G.; Zhang, X.; Dunning, F.B.; Yoshida, S.; Burgdörfer, J.We study, using a combination of experiment and theory, the excitation and decay of very-high-n(n∼280–430) strontium autoionizing Rydberg states formed by near-resonant driving of the 5s2S1/2→5p2P1/2 core-ion transition. The branching ratio between decay through radiative transitions and through autoionization is explored. Autoionization rates are measured as a function of both the nand ℓ quantum numbers of the Rydberg electron. The nonstationary decay dynamics is studied by creating and manipulating Rydberg wave packets and by varying the laser pulse that drives the core excitation.Item Characterizing high-n quasi-one-dimensional strontium Rydberg atoms(American Physical Society, 2014) Hiller, M.; Yoshida, S.; Burgdörfer, J.; Ye, S.; Zhang, X.; Dunning, F.B.; Rice Quantum InstituteThe production of high-n, n ∼ 300, quasi-one-dimensional (quasi-1D) strontium Rydberg atoms through two-photon excitation of selected extreme Stark states in the presence of a weak dc field is examined using a crossed laser-atom beam geometry. The dipolar polarization of the electron wave function in the product states is probed using two independent techniques. The experimental data are analyzed with a classical trajectory Monte Carlo simulation employing initial ensembles that are obtained with the aid of quantum calculations based on a two-active-electron model. Comparisons between theory and experiment highlight different characteristics of the product quasi-1D states, in particular, their large permanent dipole moments, ∼1.0 to 1.2n2ea0, where e is the electronic charge and a0 is the Bohr radius. Such states can be engineered using pulsed electric fields to create a wide variety of target statesItem Creating and Transporting Trojan Wave Packets(American Physical Society, 2012-01) Wyker, B.; Dunning, F.B.; Yoshida, S.; Reinhold, C.O.; Burgdörfer, J.; Rice Quantum InstituteNondispersive localized Trojan wave packets with ni 305 moving in near-circular Bohr-like orbits are created and transported to localized near-circular Trojan states of higher n, nf 600, by driving with a linearly polarized sinusoidal electric field whose period is slowly increased. The protocol is remarkably efficient with over 80% of the initial atoms being transferred to the higher n states, a result confirmed by classical trajectory Monte Carlo simulations.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 Efficient three-photon excitation of quasi-one-dimensional strontium Rydberg atoms with n ~ 300(American Physical Society, 2014) Ye, S.; Zhang, X.; Dunning, F.B.; Yoshida, S.; Hiller, M.; Burgdörfer, J.; Rice Quantum InstituteThe efficient production of very-high-n, n ~ 300, quasi-one-dimensional (quasi-1D) strontium Rydberg atoms through three-photon excitation of extreme Stark states in the presence of a weak dc field is demonstrated using a crossed laser-atom beam geometry. Strongly polarized quasi-1D states with large permanent dipole moments ∼1.2n2 a.u. can be created in the beam at densities (∼106 cm−3) where dipole blockade effects should become important. A further advantage of three-photon excitation is that the product F states are sensitive to the presence of external fields, allowing stray fields to be reduced to very small values. The experimental data are analyzed using quantum calculations based on a two-active-electron model together with classical trajectory Monte Carlo simulations. These allow determination of the atomic dipole moments and confirm that stray fields can be reduced to _25 μV cm−1.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 Production of high-n strontium Rydberg atoms(IOP Publishing, 2014) Ye, S.; Zhang, X.; Killian, T.C.; Dunning, F.B.; Hiller, M.; Yoshida, S.; Burgdörfer, J.The photoexcitation of strontium Rydberg atoms with n~300 is being examined using a crossed laser-atom beam approach to enable study of quasi-stable two-electron excited states and of strongly-coupled Rydberg systems.Item Rydberg blockade effects at n∼300 in strontium(American Physical Society, 2015) Zhang, X.; Dunning, F.B.; Yoshida, S.; Burgdörfer, J.Rydberg blockade at n∼300, is examined using strontium nF31 Rydberg atoms excited in an atomic beam in a small volume defined by two tightly focused crossed laser beams. The observation of blockade for such states is challenging due to their extreme sensitivity to stray fields and the many magnetic sublevels associated with F states which results in a high local density of states. Nonetheless, with a careful choice of laser polarization to selectively excite only a limited number of these sublevels, sizable blockade effects are observed on an ∼0.1 mm length scale extending blockade measurements into the near-macroscopic regime and enabling study of the dynamics of strongly coupled many-body high-n Rydberg systems under carefully controlled conditions.Item Rydberg blockade in a hot atomic beam(American Physical Society, 2017) Yoshida, S.; Burgdörfer, J.; Zhang, X.; Dunning, F.B.The dipole blockade of very-high-n, n∼300, strontium 5snf1F3 Rydberg atoms in a hot atomic beam is studied. For such high n, the blockade radius can exceed the linear dimensions of the excitation volume. Rydberg atoms formed inside the excitation volume can, upon leaving the region, continue to suppress excitation until they have moved farther away than the blockade radius. Moreover, the high density of states originating from the many magnetic sublevels associated with the F states results in a small but finite probability of excitation of L=3n1F3 atom pairs at small internuclear separations below the blockade radius. We demonstrate that these effects can be distinguished from one another by the distinct features they imprint on the Mandel Q parameter as a function of the duration of the exciting laser.Item Rydberg-blockade effects in Autler-Townes spectra of ultracold strontium(American Physical Society, 2016) DeSalvo, B.J.; Aman, J.A.; Gaul, C.; Pohl, T.; Yoshida, S.; Burgdörfer, J.; Hazzard, K.R.A.; Dunning, F.B.; Killian, T.C.; Rice Center for Quantum MaterialsWe present a combined experimental and theoretical study of the effects of Rydberg interactions on Autler-Townes spectra of ultracold gases of atomic strontium. Realizing two-photon Rydberg excitation via a long-lived triplet state allows us to probe the regime where Rydberg state decay presents the dominant decoherence mechanism. The effects of Rydberg interactions are observed in shifts, asymmetries, and broadening of the measured atom-loss spectra. The experiment is analyzed within a one-body density-matrix approach, accounting for interaction-induced level shifts and dephasing through nonlinear terms that approximately incorporate correlations due to the Rydberg blockade. This description yields good agreement with our experimental observations for short excitation times. For longer excitation times, the loss spectrum is altered qualitatively, suggesting additional dephasing mechanisms beyond the standard blockade mechanism based on pure van der Waals interactions.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.Item Trap losses induced by near-resonant Rydberg dressing of cold atomic gases(American Physical Society, 2016) Aman, J.A.; DeSalvo, B.J.; Dunning, F.B.; Killian, T.C.; Yoshida, S.; Burgdörfer, J.The near-resonant dressing of cold strontium gases and Bose-Einstein condensates contained in an optical dipole trap (ODT) with the 5s30s3S1 Rydberg state is investigated as a function of the effective two-photon Rabi frequency, detuning, and dressing time. The measurements demonstrate that a rapid decrease in the ground-state atom population in the ODT occurs even for weak dressing and when well detuned from resonance. This decrease is attributed to Rydberg atom excitation, which can lead to direct escape from the trap and to population of very long-lived 5s5p3P0,2 metastable states. The effects of interactions between Rydberg atoms, including those populated by blackbody radiation, are analyzed. The work has important implications when considering the use of Rydberg dressing to control the interactions between dressed ground-state atoms.Item Ultra-long-range Rydberg molecules in a divalent atomic system(American Physical Society, 2015) DeSalvo, B.J.; Aman, J.A.; Dunning, F.B.; Killian, T.C.; Sadeghpour, H.R.; Yoshida, S.; Burgdörfer, J.We report the creation of ultra-long-range Sr2 molecules comprising one ground-state 5s2 1S0 atom and one atom in a 5sns 3S1 Rydberg state for n ranging from 29 to 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation near resonant with the 5s5p 3P1 intermediate state, and their formation is detected through ground-state atom loss from the trap. The observed molecular binding energies are reproduced with the aid of first-order perturbation theory that utilizes a Fermi pseudopotential with effective s-wave and p-wave scattering lengths to describe the interaction between an excited Rydberg electron and a ground-state Sr atom.Item Ultralong-range Rydberg molecules(IOP Publishing, 2024) Dunning, F. B.; Kanungo, S. K.; Yoshida, S.Ultralong-range Rydberg molecules (ULRMs) comprise a Rydberg atom in whose electron cloud are embedded one (or more) ground-state atoms that are weakly-bound through their scattering of the Rydberg electron. The existence of such novel molecular species was first predicted theoretically in 2000 but they were not observed in the laboratory until 2009. Since that time, interest in their chemical properties, physical characteristics, and applications has increased dramatically. We discuss here recent advances in the study of ULRMs. These have yielded a wealth of information regarding low-energy electron scattering in an energy regime difficult to access using alternate techniques, and have provided a valuable probe of non-local spatial correlations in quantum gases elucidating the effects of quantum statistics. Studies in dense environments, where the Rydberg electron cloud can enclose hundreds, or even thousands, of ground-state atoms, have revealed many-body effects such as the creation of Rydberg polarons. The production of overlapping clouds of different cold atoms has enabled the creation of heteronuclear ULRMs. Indeed, the wide variety of atomic and molecular species that can now be cooled promises, through the careful choice of atomic (or molecular) species, to enable the production of ULRMs with properties tailored to meet a variety of different needs and applications.