Browsing by Author "Dunning, F.B."
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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 Dissociative electron attachment studies with hyperthermal Rydberg atoms(AIP Publishing, 2018) Buathong, S.; Dunning, F.B.Earlier studies of the velocity distributions of heavy-Rydberg ion-pair states formed in collisions between potassium Rydberg atoms with low-to-intermediate values of n, 10 ≲ n ≲ 15, and targets that attach free low-energy electrons have shown that such measurements can provide a window into the dynamics of dissociative electron capture. Here we propose that the reaction dynamics can be explored in much greater detail through studies using hyperthermal Rydberg atoms. This is demonstrated using, as an example, helium Rydberg atoms and a semi-classical Monte Carlo collision code developed specifically to model the dynamics of Rydberg electron transfer in collisions between Rydberg atoms and attaching targets. The simulations show that the outcome of collisions is sensitive not only to the lifetime and decay energetics of the excited intermediate negative ion formed upon initial Rydberg electron capture but also to the radial electron probability density distribution in the Rydberg atom itself, i.e., to its ℓ value.Item Dynamics of heavy-Rydberg ion-pair formation in K(14p,20p)-SF6, CCl4ﾠcollisions(AIP Publishing, 2014) Wang, C.H.; Kelley, M.; Buathong, S.; Dunning, F.B.The dynamics of formation of heavy-Rydberg ion-pair states throughﾠelectron transferﾠin K(np)-SF6, CCl4ﾠcollisions is examined byﾠmeasuringﾠtheﾠvelocity,ﾠangular, and bindingﾠenergyﾠdistributions of the product ion pairs. The results areﾠanalyzedﾠwith the aid of a Monte Carlo collision code that models both the initial electron capture and the subsequent evolution of the ion pairs. The model simulations are in good agreement with the experimental data and highlight the factors such asﾠRydberg atomﾠsize, the kineticﾠenergyﾠof relativeﾠmotionﾠof theﾠRydberg atomﾠand target particle, and (in the case of attaching targets that dissociate) the energetics ofﾠdissociationﾠthat can be used to control the properties of the product ion-pair states.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 Imaging the evolution of an ultracold strontium Rydberg gas(American Physical Society, 2013) McQuillen, P.; Zhang, X.; Strickler, T.; Dunning, F.B.; Killian, T.C.; Rice Quantum InstituteClouds of ultracold strontium 5s48s1S0 or 5s47d1D2 Rydberg atoms are created by two-photon excitation of laser-cooled 5s21S0 atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-ℓ) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the S states, which display isotropic attractive interactions, than for the D states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.Item Ionization of Rydberg atoms at patterned electrode arrays(American Physical Society, 2013) Pu, Y.; Dunning, F.B.; Rice Quantum InstituteLithographically patterned micrometer-scale electrode arrays are used to examine the effects of controlled surface electric fields on Rydberg-atom–surface interactions. The data show that application of modest electrode biases (∼±1 V) can lead to a transition from ionization of the incident atoms by short-range tunneling to field ionization well above the target surface. The resulting ions can be efficiently detected using ion collection fields whose strengths are substantially smaller than those required for direct field ionization pointing to the application of surface ionization in the detection of low-n Rydberg atoms. The data are analyzed with the aid of a Monte Carlo model and further demonstrate the critical role that local surface fields can play in governing the nature of atom-surface interactions.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 Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions(AIP Publishing LLC., 2016) Buathong, S.; Kelley, M.; Dunning, F.B.Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.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 Realizing topological edge states with Rydberg-atom synthetic dimensions(Springer Nature, 2022) Kanungo, S.K.; Whalen, J.D.; Lu, Y.; Yuan, M.; Dasgupta, S.; Dunning, F.B.; Hazzard, K.R.A.; Killian, T.C.; Rice Center for Quantum MaterialsA discrete degree of freedom can be engineered to match the Hamiltonian of particles moving in a real-space lattice potential. Such synthetic dimensions are powerful tools for quantum simulation because of the control they offer and the ability to create configurations difficult to access in real space. Here, in an ultracold 84Sr atom, we demonstrate a synthetic-dimension based on Rydberg levels coupled with millimeter waves. Tunneling amplitudes between synthetic lattice sites and on-site potentials are set by the millimeter-wave amplitudes and detunings respectively. Alternating weak and strong tunneling in a one-dimensional configuration realizes the single-particle Su-Schrieffer-Heeger (SSH) Hamiltonian, a paradigmatic model of topological matter. Band structure is probed through optical excitation from the ground state to Rydberg levels, revealing symmetry-protected topological edge states at zero energy. Edge-state energies are robust to perturbations of tunneling-rates that preserve chiral symmetry, but can be shifted by the introduction of on-site potentials.Item Resonant Rydberg Dressing of Alkaline-Earth Atoms via Electromagnetically Induced Transparency(American Physical Society, 2016) Gaul, C.; DeSalvo, B.J.; Aman, J.A.; Dunning, F.B.; Killian, T.C.; Pohl, T.We develop an approach to generate finite-range atomic interactions via optical Rydberg-state excitation and study the underlying excitation dynamics in theory and experiment. In contrast to previous work, the proposed scheme is based on resonant optical driving and the establishment of a dark state under conditions of electromagnetically induced transparency (EIT). Analyzing the driven dissipative dynamics of the atomic gas, we show that the interplay between coherent light coupling, radiative decay, and strong Rydberg-Rydberg atom interactions leads to the emergence of sizable effective interactions while providing remarkably long coherence times. The latter are studied experimentally in a cold gas of strontium atoms for which the proposed scheme is most efficient. Our measured atom loss is in agreement with the theoretical prediction based on binary effective interactions between the driven atoms.Item Rydberg atom scattering in K(12p)-CH3NO2 collisions: role of transient ion pair formation(IOP Publishing, 2017) Kelley, M.; Buathong, S.; Dunning, F.B.Studies of K(12p)-CH3NO2 collisions reveal unusually strong Rydberg atom scattering which is attributed to the formation of transient K+..CH3NO2 − ion-pair states.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.