4,355 research outputs found
Effect of the nearby levels on the resonance fluorescence spectrum of the atom-field interaction
We study the resonance fluorescence in the Jaynes-Cummings model when nearby
levels are taking into account. We show that the Stark shift produced by such
levels generates a displacement of the peaks of the resonance fluorescence due
to an induced effective detuning and also induces an asymmetry. Specific
results are presented assuming a coherent and a thermal fields
Stress-Induced Variations in the Stiffness of Micro- and Nanocantilever Beams
The effect of surface stress on the stiffness of cantilever beams remains an outstanding problem in the physical sciences. While numerous experimental studies report significant stiffness change due to surface stress, theoretical predictions are unable to rigorously and quantitatively reconcile these observations. In
this Letter, we present the first controlled measurements of stress-induced change in cantilever stiffness with commensurate theoretical quantification. Simultaneous measurements are also performed on equivalent clamped-clamped beams. All experimental results are quantitatively and accurately predicted using elasticity theory. We also present conclusive experimental evidence for invalidity of the longstanding and unphysical axial force model, which has been widely applied to interpret measurements using cantilever beams. Our findings will be of value in the development of micro- and nanoscale resonant mechanical sensors
A Passive Phase Noise Cancellation Element
We introduce a new method for reducing phase noise in oscillators, thereby
improving their frequency precision. The noise reduction device consists of a
pair of coupled nonlinear resonating elements that are driven parametrically by
the output of a conventional oscillator at a frequency close to the sum of the
linear mode frequencies. Above the threshold for parametric response, the
coupled resonators exhibit self-oscillation at an inherent frequency. We find
operating points of the device for which this periodic signal is immune to
frequency noise in the driving oscillator, providing a way to clean its phase
noise. We present results for the effect of thermal noise to advance a broader
understanding of the overall noise sensitivity and the fundamental operating
limits
The unusual volatile composition of the Halley-type comet 8P/Tuttle: Addressing the existence of an Inner Oort Cloud
We measured organic volatiles (CH4, CH3OH, C2H6, H2CO), CO, and water in
comet 8P/Tuttle, a comet from the Oort cloud reservoir now in a short-period
Halley-type orbit. We compare its composition with two other comets in
Halley-type orbits, and with comets of the "organics-normal" and
"organics-depleted" classes. Chemical gradients are expected in the
comet-forming region of the proto-planetary disk, and an individual comet
should reflect its specific heritage. If Halley-type comets came from the inner
Oort cloud as proposed, we see no common characteristics that could distinguish
such comets from those that were stored in the outer Oort cloud.Comment: 14 pages, including 1 figure and 2 Table
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