Electrons in Atoms

Marvin D. Girardeau

A many-atom representation has been derived in which bound atoms or molecules are described by elementary Bose or Fermi operators, the field operators for nuclei and electrons referring only to unbound particles. The Hamiltonian thus obtained contains not only nucleus-nucleus, electron-electron, and nucleus-electron Coulomb interactions, but also atom-atom, atom-nucleus, and atom-electron Coulomb and exchange interactions, including breakup and recombination terms.

R. B. Jordan

Adamantios P. Synanidis, P. A. D. Gonçalves, F. Javier Garcı́a de Abajo

Optically trapped Rydberg atoms are a suitable platform to explore quantum many-body physics mediated by long-range atom-atom interactions that can be engineered through externally applied light fields. However, this approach is limited to dipole-allowed transitions and a spatial resolution of the order of the optical wavelength. Here, we theoretically investigate the interaction between free electrons and individual Rydberg atoms as an approach to induce nondipolar transitions with subnanometer spatial precision and a substantial degree of control over the final atomic states. We observe unity-order excitation probabilities produced by a single electron for suitably chosen combinations of electron energies and electron-beam distance to the atom. We further discuss free-electron-atom entanglement and atom-atom entanglement in combination with lateral shaping of the electron followed by postselection. Our results support free electrons as powerful tools to manipulate Rydberg atoms in previously inaccessible ways.

Luca Salasnich, Francesco Lorenzi

Michael E. Jones

This thesis presents details of a new type of cold atom electron source (CAES) that uses an alternating current magneto-optical trap (AC-MOT). Cold atom electron sources produce electron bunches by threshold photoionisation from a population of laser-cooled atoms. The electrons extracted from the atoms are made into a beam which has an ultra-low transverse velocity distribution. The low velocity distribution increases the brightness and reduces the energy spread of the beam, making CAESs potential sources for future electron diffraction and electron spectroscopy studies. The newly commissioned source detailed here produces focused electron bunches with characteristic temperatures as low as 12.6 ± 0.8 K, at a rate of up to 10 Hz, and with a bunch charge of 2.2±0.2fC, comparable to other state-of-the-art cold atom electron sources. The AC-MOT CAES can also produce cold bunches with energies <200 eV, which is lower than has previously been reported for this type of source. The electrons originate from a population of laser-cooled 85Rb atoms held in an AC- MOT. The AC-MOT CAES design allows the magnetic trapping fields to be switched to zero in 32 μs, more than �ˆ�175 times faster than is possible using a comparable DC-MOT source. This means that electron bunches can be created and extracted in a magnetic field-free environment without any reduction in trap density and hence bunch charge, as occurs in conventional DC-MOT sources. The design, development, characterisation, and operation of the systems needed for the new AC-MOT CAES are detailed in this thesis. This includes details of the atom trapping system, the photoionisation system, the electron extraction system and the various timing systems for creation and characterisation of the resultant cold electron bunches. Finally, the characterisation of the AC-MOT CAES itself is presented, and the measured beam metrics are used to compare the new AC-MOT CAES with other CAES designs which are under development.

Aileen A. T. Durst, Einius Pultinevicius, Homar Rivera-Rodríguez +3 more

Recent advances in experiments using individually trapped atoms have enabled precise control over circular Rydberg electrons with exceptionally long lifetimes. We show that these giant and stable electron orbits can form toroidal lattice potentials for ultracold atoms with a period set by the electron's de Broglie wavelength. Unlike conventional static optical lattices, this electron lattice is formed via the electron-atom interaction, which mixes Rydberg circular states with opposite azimuthal phase winding into a standing electronic matter wave. The lattice phase is thereby intrinsically coupled to the atom position. For a pair of atoms, this results in ballistic tunneling motion in the two-atom spatial correlations along the ring, while the single particle dynamics is essentially free rotation. We simulate the dynamics for an experimentally realistic setting that exploits optical tweezers for individual atom control. Our results open a route toward incorporating long range atom-atom interactions mediated by a single electron and, ultimately, realizing small Bose and Fermi gases confined in these microscopic electronic atom traps.