4,617 research outputs found
Electron stripping and re-attachment at atomic centers using attosecond half-cycle pulses
We investigate the response of two three-body Coulomb systems when driven by
attosecond half-cycle pulses: The hydrogen molecular ion and the helium atom.
Using very short half-cycle pulses (HCPs) which effectively deliver ``kicks''
to the electrons, we first study how a carefully chosen sequence of HCPs can be
used to control to which of one of the two fixed atomic centers the electron
gets re-attached. Moving from one electron in two atomic centers to two
electrons in one atomic center we then study the double ionization from the
ground state of He by a sequence of attosecond time-scale HCPs, with each
electron receiving effectively a ``kick'' from each HCP. We investigate how the
net electric field of the sequence of HCPs affects the total and differential
ionization probabilities
Ultralong-Range Rydberg Molecules in a Divalent-Atomic System
We report the creation of ultralong-range Sr molecules comprising one
ground-state atom and one atom in a Rydberg state
for ranging from 29 to 36. Molecules are created in a trapped ultracold
atomic gas using two-photon excitation near resonant with the
intermediate state, and their formation is detected through ground-state atom
loss from the trap. The observed molecular binding energies are fit with the
aid of first-order perturbation theory that utilizes a Fermi pseudopotential
with effective -wave and -wave scattering lengths to describe the
interaction between an excited Rydberg electron and a ground-state Sr atom.Comment: 5 pages, 2 figure
Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC
The lifetimes and decay channels of ultralong-range Rydberg molecules created
in a dense BEC are examined by monitoring the time evolution of the Rydberg
population using field ionization. Studies of molecules with values of
principal quantum number, , in the range to 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 s, their destruction
being attributed to two main processes: formation of Sr ions through
associative ionization, and dissociation induced through -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.Comment: 9 pages, 8 figure
Quantum Accelerator Modes near Higher-Order Resonances
Quantum Accelerator Modes have been experimentally observed, and
theoretically explained, in the dynamics of kicked cold atoms in the presence
of gravity, when the kicking period is close to a half-integer multiple of the
Talbot time. We generalize the theory to the case when the kicking period is
sufficiently close to any rational multiple of the Talbot time, and thus
predict new rich families of experimentally observable Quantum Accelerator
Modes.Comment: Inaccurate reference [12] has been amende
Theory of excitation of Rydberg polarons in an atomic quantum gas
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
functional determinant theory, 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.Comment: 14 pages, 9 figures. arXiv admin note: substantial text overlap with
arXiv:1706.0371
Creation of Rydberg Polarons in a Bose Gas
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 -wave resonance in the low-energy electron-atom scattering
in Sr introduces a universal behavior in the Rydberg spectral lineshape and in
scaling of the spectral width (narrowing) with the Rydberg principal quantum
number, . Spectral features are described with a functional determinant
approach (FDA) that solves an extended Fr\"{o}hlich 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 FDA.Comment: 5 pages, 3 figure
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