3,562 research outputs found
Electromagnetic multipole theory for optical nanomaterials
Optical properties of natural or designed materials are determined by the
electromagnetic multipole moments that light can excite in the constituent
particles. In this work we present an approach to calculate the multipole
excitations in arbitrary arrays of nanoscatterers in a dielectric host medium.
We introduce a simple and illustrative multipole decomposition of the electric
currents excited in the scatterers and link this decomposition to the classical
multipole expansion of the scattered field. In particular, we find that
completely different multipoles can produce identical scattered fields. The
presented multipole theory can be used as a basis for the design and
characterization of optical nanomaterials
Loading a vapor cell magneto-optic trap using light-induced atom desorption
Low intensity white light was used to increase the loading rate of Rb
atoms into a vapor cell magneto-optic trap by inducing non-thermal desorption
of Rb atoms from the stainless steel walls of the vapor cell. An increased Rb
partial pressure reached a new equilibrium value in less than 10 seconds after
switching on the broadband light source. After the source was turned off, the
partial pressure returned to its previous value in times as short as 10
seconds.Comment: 7 pages, 6 figure
Motional sidebands and direct measurement of the cooling rate in the resonance fluorescence of a single trapped ion
Resonance fluorescence of a single trapped ion is spectrally analyzed using a
heterodyne technique. Motional sidebands due to the oscillation of the ion in
the harmonic trap potential are observed in the fluorescence spectrum. From the
width of the sidebands the cooling rate is obtained and found to be in
agreement with the theoretical prediction.Comment: 4 pages, 4 figures. Final version after minor changes, 1 figure
replaced; to be published in PRL, July 10, 200
Forces between a single atom and its distant mirror image
An excited-state atom whose emitted light is back-reflected by a distant
mirror can experience trapping forces, because the presence of the mirror
modifies both the electromagnetic vacuum field and the atom's own radiation
reaction field. We demonstrate this mechanical action using a single trapped
barium ion. We observe the trapping conditions to be notably altered when the
distant mirror is shifted by an optical wavelength. The well-localised barium
ion enables the spatial dependence of the forces to be measured explicitly. The
experiment has implications for quantum information processing and may be
regarded as the most elementary optical tweezers.Comment: 4 pages, 5 figures, published versio
Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
The problem of proton-antiproton motion in the --
system is investigated by means of the variational method. We introduce a
modified nuclear interaction through mass-scaling of the Born-Oppenheimer
potential. This improved treatment of the interaction includes the nondivergent
part of the otherwise divergent adiabatic correction and shows the correct
threshold behavior.
Using this potential we calculate the vibrational energy levels with angular
momentum 0 and 1 and the corresponding nuclear wave functions, as well as the
S-wave scattering length. We obtain a full set of all bound states together
with a large number of discretized continuum states that might be utilized in
variational four-body calculations. The results of our calculations gives an
indication of resonance states in the hydrogen-antihydrogen system
Optomechanical Cooling of a Macroscopic Oscillator by Homodyne Feedback
We propose a simple optomechanical model in which a mechanical oscillator
quadrature could be "cooled" well below its equilibrium temperature by applying
a suitable feedback to drive the orthogonal quadrature by means of the homodyne
current of the radiation field used to probe its position.Comment: 9 pages, RevTeX, Figures available from authors, to appear in Phys.
Rev. Let
Atomic multipole relaxation rates near surfaces
The spontaneous relaxation rates for an atom in free space and close to an
absorbing surface are calculated to various orders of the electromagnetic
multipole expansion. The spontaneous decay rates for dipole, quadrupole and
octupole transitions are calculated in terms of their respective primitive
electric multipole moments and the magnetic relaxation rate is calculated for
the dipole and quadrupole transitions in terms of their respective primitive
magnetic multipole moments. The theory of electromagnetic field quantization in
magnetoelectric materials is used to derive general expressions for the decay
rates in terms of the dyadic Green function. We focus on the decay rates in
free space and near an infinite half space. For the decay of atoms near to an
absorbing dielectric surface we find a hierarchy of scaling laws depending on
the atom-surface distance z.Comment: Updated to journal version. 16 page
Gravitational wave astronomy
The first decade of the new millenium should see the first direct detections
of gravitational waves. This will be a milestone for fundamental physics and it
will open the new observational science of gravitational wave astronomy. But
gravitational waves already play an important role in the modeling of
astrophysical systems. I review here the present state of gravitational
radiation theory in relativity and astrophysics, and I then look at the
development of detector sensitivity over the next decade, both on the ground
(such as LIGO) and in space (LISA). I review the sources of gravitational waves
that are likely to play an important role in observations by first- and
second-generation interferometers, including the astrophysical information that
will come from these observations. The review covers some 10 decades of
gravitational wave frequency, from the high-frequency normal modes of neutron
stars down to the lowest frequencies observable from space. The discussion of
sources includes recent developments regarding binary black holes, spinning
neutron stars, and the stochastic background.Comment: 29 pages, 2 figures, as submitted for special millenium issue of
Classical and Quantum Gravit
Magnetic trapping of metastable atomic strontium
We report the magnetic trapping of metastable atomic strontium. Atoms
are cooled in a magneto-optical trap (MOT) operating on the dipole allowed
transition at 461 nm. Decay via
continuously loads a magnetic trap formed by the quadrupole magnetic field of
the MOT. Over atoms at a density of cm and
temperature of 1 mK are trapped. The atom temperature is significantly lower
than what would be expected from the kinetic and potential energy of atoms as
they are transferred from the MOT. This suggests that thermalization and
evaporative cooling are occurring in the magnetic trap.Comment: This paper has been accepted by PR
Measurements of Lifetimes and a Limit on the Lifetime Difference in the Neutral D-Meson System
Using the large hadroproduced charm sample collected in experiment E791 at
Fermilab, we report the first directly measured constraint on the decay-width
difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We
obtain our result from lifetime measurements of the decays D0 --> K-pi+ and D0
--> K-K+, under the assumption of CP invariance, which implies that the CP
eigenstates and the mass eigenstates are the same. The lifetime of D0 --> K-K+
(the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the
lifetime of D0 --> K-pi+ (an equal mixture of CP-odd and CP-even final states
is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta
Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these
measurements to measurements of mixing in the neutral D-meson system.Comment: 8 pages + 3 figures + 2 table
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