1,484 research outputs found
Laser radiation pressure slowing of a molecular beam
There is substantial interest in producing samples of ultracold molecules for
possible applications in quantum computation, quantum simulation of condensed
matter systems, precision measurements, controlled chemistry, and high
precision spectroscopy. A crucial step to obtaining large samples of ultracold,
trapped molecules is developing a means to bridge the gap between typical
molecular source velocities (~150-600 m/s) and velocities for which trap
loading or confinement is possible (~5-20 m/s). Here we show deceleration of a
beam of neutral strontium monofluoride (SrF) molecules using radiative force.
Under certain conditions, the deceleration results in a substantial flux of
molecules with velocities <50 m/s. The observed slowing, from ~140 m/s,
corresponds to scattering ~10000 photons. We also observe longitudinal velocity
compression under different conditions. Combined with molecular laser cooling
techniques, this lays the groundwork to create slow and cold molecular beams
suitable for trap loading.Comment: 7 pages, 7 figures. Supplementary material updated
Scaling by 5 on a 1/4-Cantor Measure
Each Cantor measure (\mu) with scaling factor 1/(2n) has at least one
associated orthonormal basis of exponential functions (ONB) for L^2(\mu). In
the particular case where the scaling constant for the Cantor measure is 1/4
and two specific ONBs are selected for L^2(\mu), there is a unitary operator U
defined by mapping one ONB to the other. This paper focuses on the case in
which one ONB (\Gamma) is the original Jorgensen-Pedersen ONB for the Cantor
measure (\mu) and the other ONB is is 5\Gamma. The main theorem of the paper
states that the corresponding operator U is ergodic in the sense that only the
constant functions are fixed by U.Comment: 34 page
Professional Concerns
In the contribution which follows, Collett B. Dilworth, Jr., of the English Department at East Carolina University, gets to the very heart of why literature is taught in schools. He broaches the question of how literary study relates to the basic skills, and he ties his rationale in with questions of accountability and its handmaiden, competency testing. Probably the heart of Dilworth\u27s argument is in his statement, The student of literature is not primarily looking for information, s/he is looking for experience
Franck-Condon Factors and Radiative Lifetime of the A^{2}\Pi_{1/2} - X^{2}\Sigma^{+} Transition of Ytterbium Monoflouride, YbF
The fluorescence spectrum resulting from laser excitation of the
A^{2}\Pi_{1/2} - X^{2}\Sigma^{+} (0,0) band of ytterbium monofluoride, YbF, has
been recorded and analyzed to determine the Franck-Condon factors. The measured
values are compared with those predicted from Rydberg-Klein-Rees (RKR)
potential energy curves. From the fluorescence decay curve the radiative
lifetime of the A^{2}\Pi_{1/2} state is measured to be 28\pm2 ns, and the
corresponding transition dipole moment is 4.39\pm0.16 D. The implications for
laser cooling YbF are discussed.Comment: 5 pages, 5 figure
Centennial-to-millennial hydrologic trends and variability along the North Atlantic Coast, USA, during the Holocene
Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 4300–4307, doi:10.1002/2014GL060183.Geophysical and sedimentary records from five lakes in Massachusetts reveal regionally coherent hydrologic variability during the Holocene. All of the lakes have risen since ~9.0 ka, but multicentury droughts after 5.6 ka repeatedly lowered their water levels. Quantified water level histories from the three best-studied lakes share >70% of their reconstructed variance. Four prominent low-water phases at 4.9–4.6, 4.2–3.9, 2.9–2.1, and 1.3–1.2 ka were synchronous across coastal lakes, even after accounting for age uncertainties. The droughts also affected sites up to ~200 km inland, but water level changes at 5.6–4.9 ka appear out of phase between inland and coastal lakes. During the enhanced multicentury variability after ~5.6 ka, droughts coincided with cooling in Greenland and may indicate circulation changes across the North Atlantic region. Overall, the records demonstrate that current water levels are exceptionally high and confirm the sensitivity of water resources in the northeast U.S. to climate change.The National Science
Foundation (EAR-0602408, EAR-
1036191, and DEB-0816731 to Shuman;
EAR-0602380 to Donnelly) and the
Woods Hole Oceanographic Institution,
Ocean and Climate Change Institute
(Donnelly) funded this research.2014-12-2
Mars Orbiter Study. Volume 2: Mission Design, Science Instrument Accommodation, Spacecraft Design
Spacecraft system and subsystem designs were developed at the conceptual level to perform either of two Mars Orbiter Missions, a Climatology Mission and an Aeronomy Mission. The objectives of these missions are to obtain and return data to increase knowledge of Mars
Electrically Evoked Auditory Event-Related Responses in Patients with Auditory Brainstem Implants: Morphological Characteristics, Test–Retest Reliability, Effects of Stimulation Level, and Association with Auditory Detection
This study aimed to 1) characterize morphological characteristics of the electrically-evoked cortical auditory event-related potentials (eERP) and explore the potential association between onset eERP morphology and auditory vs non-auditory stimulation; 2) assess test-retest reliability of onset eERPs; 3) investigate effects of stimulation level on onset eERPs; and 4) explore the feasibility of using the onset eERP to estimate the lowest stimulation level that can be detected for individual stimulating electrodes in patients with auditory brainstem implants (ABIs)
Stark deceleration of CaF molecules in strong- and weak-field seeking states
We report the Stark deceleration of CaF molecules in the strong-field seeking
ground state and in a weak-field seeking component of a rotationally-excited
state. We use two types of decelerator, a conventional Stark decelerator for
the weak-field seekers, and an alternating gradient decelerator for the
strong-field seekers, and we compare their relative merits. We also consider
the application of laser cooling to increase the phase-space density of
decelerated molecules.Comment: 10 pages, 8 figure
Destabilizing effects of visual environment motions simulating eye movements or head movements
In the present paper, we explore effects on the human of exposure to a visual virtual environment which has been enslaved to simulate the human user's head movements or eye movements. Specifically, we have studied the capacity of our experimental subjects to maintain stable spatial orientation in the context of moving their entire visible surroundings by using the parameters of the subjects' natural movements. Our index of the subjects' spatial orientation was the extent of involuntary sways of the body while attempting to stand still, as measured by translations and rotations of the head. We also observed, informally, their symptoms of motion sickness
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