A New Perspective on the Binding Power of an Electron

Hogan, S. D.; Merkt, F.

doi:10.1002/cphc.200900499

Cited by 5 publications

(4 citation statements)

References 35 publications

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“…In these states, an atom in its electronic ground state is located inside the large electron orbit of a Rydberg atom with which it interacts via the slow Rydberg electron. This binding mechanism does not fit into the usual categories of chemical bonds, namely covalent, ionic, metallic or van der Waals [35]. Two main sub-classes of these long-range molecular states were already predicted in Ref.…”

Section: Long-range Rydberg Moleculesmentioning

confidence: 81%

Long-range Rydberg molecules, Rydberg macrodimers and Rydberg aggregates in an ultracold Cs gas

Saßmannshausen

Deiglmayr

Merkt

2016

Eur. Phys. J. Spec. Top.

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We present an overview of our recent investigations of longrange interactions in an ultracold Cs Rydberg gas. These interactions are studied by high-resolution photoassociation spectroscopy, using excitation close to one-photon transitions into np 3/2 Rydberg states with pulsed and continuous-wave ultraviolet laser radiation, and lead to the formation of long-range Cs2 molecules. We observe two types of molecular resonances. The first type originates from the correlated excitation of two atoms into Rydberg-atom-pair states interacting at long range via multipole-multipole interactions. The second type results from the interaction of one atom excited to a Rydberg state with one atom in the electronic ground state. Which type of resonances is observed in the experiments depends on the laser intensity and frequency and on the pulse sequences used to prepare the Rydberg states. We obtain insights into both types of molecular resonances by modelling the interaction potentials, using a multipole expansion of the long-range interaction for the first type of resonances and a Fermi-contact pseudo-potential for the second type of resonances. We analyse the relation of these long-range molecular resonances to molecular Rydberg states and ionpair states, and discuss their decay channels into atomic and molecular ions. In experiments carried out with a two-colour two-photon excitation scheme, we observe a large enhancement of Rydberg-excitation probability, which we interpret as a saturable autocatalytic antiblockade phenomenon.

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Section: Long-range Rydberg Moleculesmentioning

confidence: 81%

Long-range Rydberg molecules, Rydberg macrodimers and Rydberg aggregates in an ultracold Cs gas

Saßmannshausen

Deiglmayr

Merkt

2016

Eur. Phys. J. Spec. Top.

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“…Their distinctive binding mechanism, which is unlike conventional covalent, ionic, and van der Waals bonds between ground-state atoms, results in loosely bound molecules whose properties closely mimic those of their constituent Rydberg atoms. The discovery of these molecular bonds has been likened to a new ultracold chemistry [3], and has spurred a significant amount of theoretical [4,5] and experimental interest [6][7][8][9]. Non-degenerate, low angular momentum Rydberg states (orbital angular momentum ℓ ≤ 2 in rubidium) produce molecules with a few tens of MHz binding energies and permanent electric dipole moments of a few Debye.…”

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confidence: 99%

Photoassociation of Long-RangenDRydberg Molecules

2014

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We observe long-range homonuclear diatomic nD Rydberg molecules photoassociated out of an ultracold gas of 87 Rb atoms for 34≤ n ≤40. The measured ground-state binding energies of 87 Rb(nD − 5S 1/2 ) molecular states are larger than those of their 87 Rb(nS − 5S 1/2 ) counterparts, showing the dependence of the molecular bond on the angular momentum of the Rydberg atom. We exhibit the transition of 87 Rb(nD − 5S 1/2 ) molecules from a molecular-binding-dominant regime at low n to a fine-structure-dominant regime at high n [akin to Hund's cases (a) and (c), respectively]. In the analysis the fine structure of the nD Rydberg atom and the hyperfine structure of the 5S 1/2 atom are included.PACS numbers: 34.50. Cx,34.20.Cf,33.80.Rv,31.10.+z, Cold atomic systems have opened new frontiers at the interface of atomic and molecular physics. Of particular interest are a recently discovered class of long-range, homonuclear Rydberg molecules [1,2]. Formed via an attractive interaction between a Rydberg electron and a ground-state atom [1], these molecules are among the largest ever observed with internuclear separations of several thousand Bohr radii. Their distinctive binding mechanism, which is unlike conventional covalent, ionic, and van der Waals bonds between ground-state atoms, results in loosely bound molecules whose properties closely mimic those of their constituent Rydberg atoms. The discovery of these molecular bonds has been likened to a new ultracold chemistry [3], and has spurred a significant amount of theoretical [4,5] and experimental interest [6][7][8][9]. Non-degenerate, low angular momentum Rydberg states (orbital angular momentum ℓ ≤ 2 in rubidium) produce molecules with a few tens of MHz binding energies and permanent electric dipole moments of a few Debye. The ℓ = 0 molecules were first observed by photoassociation [10] The relevant interaction was first described by Fermi [11] to help explain pressure-induced energy shifts of Rydberg absorption lines in a gas [12]. The deBroglie wavelength of the Rydberg electron (position r) is much larger than that of a heavy ground-state atom (position R) that lies within the Rydberg atom's volume, and their interaction can be approximated as a low-energy s-wave scattering process (scattering length a s ). The interaction is described with a Fermi-type pseudopotential [1,13], V pseudo (r) = 2πa s δ 3 (r − R), where p-wave and higherorder scattering [4] are neglected. For negative a s the interaction can lead to bound molecular states [1,13].In the present work we focus on long-range 87 Rb 2 molecules formed by an nD Rydberg and a 5S 1/2 ground state atom. The binding energies generally increase with ℓ, due to the √ 2ℓ + 1-scaling of the Y m=0 l (θ = 0). Among the low-ℓ variety of these molecules the nD ones have the highest binding energies. The angular-momentum coupling spans three Hund's cases when varying ℓ from 0 to 2. The nS 1/2 − 5S 1/2 molecules are akin to Hund's case (b), because they have L = 0 and total electron spin S = 1. The nP j − 5S 1/2 molecules a...

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“…The bond between the Rydberg atom and the ground-state atom originates from the attractive interaction between the Rydberg electron and the ground-state atom [1]. This bond has been described as a new type of chemical bond, distinct from the wellknown covalent, ionic, and van der Waals bonds [2]. The name "trilobite molecule" was coined because in certain states, the perturbed Rydberg-electron wavefunction resembles a trilobite fossil [1].…”

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confidence: 99%

Excitation of Weakly Bound Molecules to Trilobitelike Rydberg States

et al. 2013

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We observe "trilobite-like" states of ultracold 85 Rb2 molecules, in which a ground-state atom is bound by the electronic wavefunction of its Rydberg-atom partner. We populate these states through the ultraviolet excitation of weakly-bound molecules, and access a regime of trilobite-like states at low principal quantum numbers and with vibrational turning points around 35 Bohr radii. This demonstrates that, unlike previous studies that used free-to-bound transitions, trilobite-like states can also be excited through bound-to-bound transitions. This approach provides high excitation probabilities without requiring high-density samples, and affords the ability to control the excitation radius by selection of the initial-state vibrational level.PACS numbers: 33.80. Rv, 33.20.Lg, 31.10.+z A class of long-range Rydberg molecules, sometimes called "trilobite molecules," occurs when a ground-state atom is embedded within the electronic wavefunction of a Rydberg atom [1]. The bond between the Rydberg atom and the ground-state atom originates from the attractive interaction between the Rydberg electron and the ground-state atom [1]. This bond has been described as a new type of chemical bond, distinct from the wellknown covalent, ionic, and van der Waals bonds [2]. The name "trilobite molecule" was coined because in certain states, the perturbed Rydberg-electron wavefunction resembles a trilobite fossil [1]. Trilobite states are characterized by large, and degenerate, values of orbital angular momentum (l ≥ 3) and large permanent electric dipole moments (EDMs ∼ 1 kDebye). Although pure trilobite states have yet to be observed, trilobite-like states, bound by the same novel chemical bond but characterized primarily by lower values of l and smaller EDMs, have been observed at ultracold temperature in photoassociation to bound vibrational levels [3][4][5][6][7][8], and at high temperatures in the form of satellite structures in the wings of atomic transitions [9,10].We adopt the name "trilobite-like" molecules for the low-l states to distinguish them from other types of longrange Rydberg molecules, such as macrodimers [11][12][13] or heavy Rydberg atoms [14,15].The bond length of a trilobite-like molecule can vary greatly depending on the principal quantum number, due to the n 2 dependence of the radius of the outermost lobe of the Rydberg wavefunction. For instance, the vibrational outer turning points of trilobite-like molecules have ranged from below 150 Bohr radii (a 0 ) in Refs. [9, 10] to above 10 3 a 0 in Refs. [3][4][5][6][7][8].Here we report the observation of trilobite-like states of 85 Rb 2 by a new method. We start by producing ultracold Rb 2 molecules in a high vibrational level of the metastable a 3 Σ + u state via photoassociation of atoms in a magneto-optical trap (MOT), then excite them directly to trilobite-like states, detecting them via their autoionization into Rb + 2 molecular ions. We observe these states in some of the lowest principal quantum numbers for which they can exist, n = 7 and 9-12, and...

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A New Perspective on the Binding Power of an Electron

Cited by 5 publications

References 35 publications

Long-range Rydberg molecules, Rydberg macrodimers and Rydberg aggregates in an ultracold Cs gas

Long-range Rydberg molecules, Rydberg macrodimers and Rydberg aggregates in an ultracold Cs gas

Photoassociation of Long-RangenDRydberg Molecules

Excitation of Weakly Bound Molecules to Trilobitelike Rydberg States

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