1,714 research outputs found
The plasmonic eigenvalue problem
A plasmon of a bounded domain is a non-trivial
bounded harmonic function on which is
continuous at and whose exterior and interior normal
derivatives at have a constant ratio. We call this ratio a
plasmonic eigenvalue of . Plasmons arise in the description of
electromagnetic waves hitting a metallic particle . We investigate
these eigenvalues and prove that they form a sequence of numbers converging to
one. Also, we prove regularity of plasmons, derive a variational
characterization, and prove a second order perturbation formula. The problem
can be reformulated in terms of Dirichlet-Neumann operators, and as a side
result we derive a formula for the shape derivative of these operators.Comment: 22 pages; replacement 8-March-14: minor corrections; to appear in
Review in Mathematical Physic
Perturbation theory for plasmonic eigenvalues
We develop a perturbative approach for calculating, within the quasistatic
approximation, the shift of surface resonances in response to a deformation of
a dielectric volume. Our strategy is based on the conversion of the homogeneous
system for the potential which determines the plasmonic eigenvalues into an
inhomogeneous system for the potential's derivative with respect to the
deformation strength, and on the exploitation of the corresponding
compatibility condition. The resulting general expression for the first-order
shift is verified for two explicitly solvable cases, and for a realistic
example of a deformed nanosphere. It can be used for scanning the huge
parameter space of possible shape fluctuations with only quite small
computational effort
Ion-lithium collision dynamics studied with an in-ring MOTReMi
We present a novel experimental tool allowing for kinematically complete
studies of break-up processes of laser-cooled atoms. This apparatus, the
'MOTReMi', is a combination of a magneto-optical trap (MOT) and a Reaction
Microscope (ReMi). Operated in an ion-storage ring, the new setup enables to
study the dynamics in swift ion-atom collisions on an unprecedented level of
precision and detail. In first experiments on collisions with 1.5 MeV/amu
O-Li the pure ionization of the valence electron as well as
ionization-excitation of the lithium target has been investigated
Tests of relativity using a microwave resonator
The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are
compared to set new constraints on a possible violation of Lorentz invariance.
We determine the variation of the oscillator frequency as a function of its
orientation (Michelson-Morley test) and of its velocity (Kennedy-Thorndike
test) with respect to a preferred frame candidate. We constrain the
corresponding parameters of the Mansouri and Sexl test theory to and which is equivalent to the best previous result for the
former and represents a 30 fold improvement for the latter.Comment: 8 pages, 2 figures, submitted to Physical Review Letters (October 3,
2002
Cooling of Molecular Ion Beams
An overview of the use of stored ion beams and phase space cooling (electron cooling) is given for the field of molecular physics. Emphasis is given to interactions between molecular ions and electrons studied in the electron cooler: dissociative recombination and, for internally excited molecular ions, electron-induced ro-vibrational cooling. Diagnostic methods for the transverse ion beam properties and for the internal exciation of the molecular ions are discussed, and results for phase space cooling and internal (vibrational) cooling are presented for hydrogen molecular ions
A general approximation of quantum graph vertex couplings by scaled Schroedinger operators on thin branched manifolds
We demonstrate that any self-adjoint coupling in a quantum graph vertex can
be approximated by a family of magnetic Schroedinger operators on a tubular
network built over the graph. If such a manifold has a boundary, Neumann
conditions are imposed at it. The procedure involves a local change of graph
topology in the vicinity of the vertex; the approximation scheme constructed on
the graph is subsequently `lifted' to the manifold. For the corresponding
operator a norm-resolvent convergence is proved, with the natural
identification map, as the tube diameters tend to zero.Comment: 19 pages, one figure; introduction amended and some references added,
to appear in CM
Radiative rotational lifetimes and state-resolved relative detachment cross sections from photodetachment thermometry of molecular anions in a cryogenic storage ring
Photodetachment thermometry on a beam of OH in a cryogenic storage ring
cooled to below 10 K is carried out using two-dimensional, frequency and time
dependent photodetachment spectroscopy over 20 minutes of ion storage. In
equilibrium with the low-level blackbody field, we find an effective radiative
temperature near 15 K with about 90% of all ions in the rotational ground
state. We measure the J = 1 natural lifetime (about 193 s) and determine the
OH rotational transition dipole moment with 1.5% uncertainty. We also
measure rotationally dependent relative near-threshold photodetachment cross
sections for photodetachment thermometry.Comment: Manuscript LaTeX with 5 pages, 3 figures, and 1 table plus LaTeX
supplement with 12 pages, 3 figures and 3 tables. This article has been
accepted by Physical Review Letter
The acceleration and storage of radioactive ions for a neutrino factory
The term beta-beam has been coined for the production of a pure beam of
electron neutrinos or their antiparticles through the decay of radioactive ions
circulating in a storage ring. This concept requires radioactive ions to be
accelerated to a Lorentz gamma of 150 for 6He and 60 for 18Ne. The neutrino
source itself consists of a storage ring for this energy range, with long
straight sections in line with the experiment(s). Such a decay ring does not
exist at CERN today, nor does a high-intensity proton source for the production
of the radioactive ions. Nevertheless, the existing CERN accelerator
infrastructure could be used as this would still represent an important saving
for a beta-beam facility. This paper outlines the first study, while some of
the more speculative ideas will need further investigations.Comment: Accepted for publication in proceedings of Nufact02, London, 200
Dielectronic Recombination of Ground-State and Metastable Li+ Ions
Dielectronic recombination has been investigated for Delta-n = 1 resonances
of ground-state Li+(1s^2) and for Delta-n = 0 resonances of metastable Li+(1s2s
^3S). The ground-state spectrum shows three prominent transitions between 53
and 64 eV, while the metastable spectrum exhibits many transitions with
energies < 3.2 eV. Reasonably good agreement of R-matrix, LS coupling
calculations with the measured recombination rate coefficient is obtained. The
time dependence of the recombination rate yields a radiative lifetime of 52.2
+- 5.0 s for the 2 ^3S level of Li+.Comment: Submitted to Phys. Rev. A; REVTeX, 4 pages, 3 figure
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