156 research outputs found
Complex non-equilibrium dynamics in plasmas
Two new forms of strongly coupled plasmas will be discussed. They have become
possible to create and observe in the laboratory only recently and exhibit a
wealth of intriguing complex behavior which can be studied, in many cases for
the first time, experimentally. Plasmas, gases of charged particles, are
universal in the sense that certain properties of complex behavior do only
depend on ratios of characteristic parameters of the plasma, not on the
parameters themselves. Therefore, it is of fundamental and far reaching
consequence, to be able to create and observe a strongly coupled plasma since
its behavior is paradigmatic for an entire class of plasmas.Comment: 14 pages, to be published in European Revie
Attosecond light pulse induced photo-association
We explore stimulated photo-association in the context of attosecond
pump-probe schemes of atomic matter. An attosecond pulse -- the probe -- is
used to induce photo-association of an electronic wave packet which had been
created before, typically with an attosecond pump pulse at an atomic center
different from the one of photo-association. We will show that the electron
absorption is maximal for a certain delay between the pulses. Two ways of
enhancing and controlling stimulated photo-association are proposed, namely
using an additional infrared pulse to steer the electronic wave packet and
using a train of attosecond pulses instead of a single pair. A direct
application of ultrafast stimulated photo-association is the measurement of
atomic distances.Comment: 7 pages, 8 figure
Floquet approach for dynamics in short and intense laser pulses
We present a two-timescale Floquet method that allows one to apply the
Kramers-Henneberger approach to short pulses and arbitrary laser frequencies.
An efficient numerical procedure to propagate the Floquet Hamiltonian is
provided that relies on the Toeplitz matrix formalism and Fast Fourier
Transformations. It enables efficient time propagation with large Floquet
expansions, while still taking advantage of the cycle-averaged
Kramers-Henneberger basis. Three illustrative cases of ionization with
different photon energies are analyzed, where the envelope of a short and
intense pulse is crucial to the underlying dynamics.Comment: 39 pages, 11 figure
Polyatomic trilobite Rydberg molecules in a dense random gas
Trilobites are exotic giant dimers with enormous dipole moments. They consist
of a Rydberg atom and a distant ground-state atom bound together by short-range
electron-neutral attraction. We show that highly polar, polyatomic trilobite
states unexpectedly persist and thrive in a dense ultracold gas of randomly
positioned atoms. This is caused by perturbation-induced quantum scarring and
the localization of electron density on randomly occurring atom clusters. At
certain densities these states also mix with a s-state, overcoming selection
rules that hinder the photoassociation of ordinary trilobites
Polyatomic trilobite Rydberg molecules in a dense random gas
Trilobites are exotic giant dimers with enormous dipole moments. They consist
of a Rydberg atom and a distant ground-state atom bound together by short-range
electron-neutral attraction. We show that highly polar, polyatomic trilobite
states unexpectedly persist and thrive in a dense ultracold gas of randomly
positioned atoms. This is caused by perturbation-induced quantum scarring and
the localization of electron density on randomly occurring atom clusters. At
certain densities these states also mix with a s-state, overcoming selection
rules that hinder the photoassociation of ordinary trilobites
Proton ejection from molecular hydride clusters exposed to strong X-ray pulses
Clusters consisting of small molecules containing hydrogen do eject fast
protons when illuminated by short X-ray pulses. A suitable overall charging of
the cluster controlled by the X-ray intensity induces electron migration from
the surface to the bulk leading to efficient segregation of the protons and to
a globally hindered explosion of the heavy atoms even outside the screened
volume. We investigate this peculiar effect systematically along the
iso-electronic sequence of methane over ammonia and water to the atomic limit
of neon as a reference. In contrast to core-shell systems where the outer shell
is sacrificed to reduce radiation damage, the intricate proton dynamics of
hydride clusters allows one to keep the entire backbone of heavy atoms intact.Comment: 5 pages, 5 figure
Break-up of Rydberg superatoms via dipole-dipole interactions
We investigate resonant dipole-dipole interactions between two "superatoms"
of different angular momentum, consisting of two Rydberg-blockaded atom clouds
where each of them carries initially a coherently shared single excitation. We
demonstrate that the dipole-dipole interaction breaks up the superatoms by
removing the excitations from the clouds. The dynamics is akin to an ensemble
average over systems where only one atom per cloud participates in entangled
motion and excitation transfer. Our findings should thus facilitate the
experimental realization of adiabatic exciton transport in Rydberg systems by
replacing single sites with atom clouds.Comment: 10 pages, 5 figure
Non-adiabatic molecular association in thermal gases driven by radio-frequency pulses
The molecular association process in a thermal gas of Rb is
investigated where the effects of the envelope of the radio-frequency field are
taken into account. For experimentally relevant parameters our analysis shows
that with increasing pulse length the corresponding molecular conversion
efficiency exhibits low-frequency interference fringes which are robust under
thermal averaging over a wide range of temperatures. This dynamical
interference phenomenon is attributed to St\"uckelberg phase accumulation
between the low-energy continuum states and the dressed molecular state which
exhibits a shift proportional to the envelope of the radio-frequency pulse
intensity.Comment: 5 pages, 3 figure
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