1,618 research outputs found
Pumped quantum systems: immersion fluids of the future?
Quantum optical techniques may yield immersion fluids with high indices of
refraction without absorption. We describe one such technique in which a probe
field experiences a large index of refraction with amplification rather than
absorption, and examine its practicality for an immersion lithography
application. Enhanced index can be observed in a three-level system with a
tunable, near-resonant, coherent probe and incoherent pump field that inverts
population of the probe transition. This observation contradicts the common
belief that large indices of refraction are impossible without absorption,
however it is well in accord with existing electromagnetic theory and practice.
Calculations show that a refractive index >> 2 is possible with practical
experimental parameters. A scheme with an incoherent mixture of pumped and
unpumped atoms is also examined, and is seen to have a lower refractive index
(~2) accompanied by neither gain nor loss.Comment: 6 pages, 7 figures, accepted for publication in J. Vac. Sci. Tech. B,
Nov/Dec 2005 (full reference not known yet
Demonstrating Universal Scaling in Quench Dynamics of a Yukawa One-Component Plasma
The Yukawa one-component plasma (OCP) is a paradigm model for describing
plasmas that contain one component of interest and one or more other components
that can be treated as a neutralizing, screening background. In appropriately
scaled units, interactions are characterized entirely by a screening parameter,
. As a result, systems of similar show the same dynamics,
regardless of the underlying parameters (e.g., density and temperature). We
demonstrate this behavior using ultracold neutral plasmas (UNP) created by
photoionizing a cold ( mK) gas. The ions in UNP systems are well
described by the Yukawa model, with the electrons providing the screening.
Creation of the plasma through photoionization can be thought of as a rapid
quench from to a final value set by the electron
density and temperature. We demonstrate experimentally that the post-quench
dynamics are universal in over a factor of 30 in density and an order
of magnitude in temperature. Results are compared with molecular dynamics
simulations. We also demonstrate that features of the post-quench kinetic
energy evolution, such as disorder-induced heating and kinetic-energy
oscillations, can be used to determine the plasma density and the electron
temperature.Comment: 10 pages, 12 figures, to be submitted to Physical Review
High Resolution Ionization of Ultracold Neutral Plasmas
Collective effects, such as waves and instabilities, are integral to our
understanding of most plasma phenomena. We have been able to study these in
ultracold neutral plasmas by shaping the initial density distribution through
spatial modulation of the ionizing laser intensity. We describe a relay imaging
system for the photoionization beam that allows us to create higher resolution
features and its application to extend the observation of ion acoustic waves to
shorter wavelengths. We also describe the formation of sculpted density
profiles to create fast expansion of plasma into vacuum and streaming plasmas
Seeking Sustainability: COSA preliminary analysis of sustainability initiatives in the coffee sector
The growing economic value and consumer popularity of sustainability standards inevitably raise questions about the extent to which their structure and dynamics actually address many environmental, economic and public welfare issues. The Committee on Sustainable Assessment (COSA) was formed, in part, to develop a scientifically credible framework capable of assessing the impacts associated with the adoption of sustainability initiatives. This paper examines the pilot phase of vetting and testing the COSA method, an innovative management tool used to gather and analyze data using economic, environmental and social metrics.sustainability initiatives, standards, organic, fair trade, Rainforest, social, environmental, economic certification
An Evaluation of Avian Influenza Virus Whole-Genome Sequencing Approaches Using Nanopore Technology
As exemplified by the global response to the SARS-CoV-2 pandemic, whole-genome sequencing played an important role in monitoring the evolution of novel viral variants and provided guidance on potential antiviral treatments. The recent rapid and extensive introduction and spread of highly pathogenic avian influenza virus in Europe, North America, and elsewhere raises the need for similarly rapid sequencing to aid in appropriate response and mitigation activities. To facilitate this objective, we investigate a next-generation sequencing platform that uses a portable nanopore sequencing device to generate and present data in real time. This platform offers the potential to extend in-house sequencing capacities to laboratories that may otherwise lack resources to adopt sequencing technologies requiring large benchtop instruments. We evaluate this platform for routine use in a diagnostic laboratory. In this study, we evaluate different primer sets for the whole genome amplification of influenza A virus and evaluate five different library preparation approaches for sequencing on the nanopore platform using the MinION flow cell. A limited amplification procedure and a rapid procedure are found to be best among the approaches taken
Combined molecular dynamics and quantum trajectories simulation of laser-driven, collisional systems
We introduce a combined molecular dynamics (MD) and quantum trajectories (QT)
code to simulate the effects of near-resonant optical fields on state-vector
evolution and particle motion in a collisional system. In contrast to
collisionless systems, in which the quantum dynamics of multi-level,
laser-driven particles with spontaneous emission can be described with the
optical Bloch equations (OBEs), particle velocities in sufficiently collisional
systems change on timescales comparable to those of the laser-induced,
quantum-state dynamics. These transient velocity changes can cause the
time-averaged velocity dependence of the quantum state to differ from the OBE
solution. We use this multiscale code to describe laser-cooling in a strontium
ultracold neutral plasma. Important phenomena described by the simulation
include suppression of electromagnetically induced transparencies through rapid
velocity changing collisions and thermalization between cooled and un-cooled
directions for anisotropic laser cooling.Comment: 14 pages, 10 figure
Probing Nonlocal Spatial Correlations in Quantum Gases with Ultra-long-range Rydberg Molecules
We present photo-excitation of ultra-long-range Rydberg molecules as a probe
of spatial correlations in quantum gases. Rydberg molecules can be created with
well-defined internuclear spacing, set by the radius of the outer lobe of the
Rydberg electron wavefunction . By varying the principal quantum number
of the target Rydberg state, the molecular excitation rate can be used to
map the pair-correlation function of the trapped gas . We
demonstrate this with ultracold Sr gases and probe pair-separation length
scales ranging from , which are on the order of the
thermal de Broglie wavelength for temperatures around 1 K. We observe
bunching for a single-component Bose gas of Sr and anti-bunching due to
Pauli exclusion at short distances for a polarized Fermi gas of Sr,
revealing the effects of quantum statistics.Comment: 6 pages, 5 figure
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