15,022 research outputs found
Laboratory studies of infrared absorption by NO2 and HNO3
Data concerning the quantitative absorption in the 11 and 22 micron region by HNO3 were obtained. Results are presented indicating the temperature dependence of these bands of HNO3 vapor. The 21.8 micron absorption bands of HNO3 vapor at 40 C are discussed along with the integrated intensity and line parameters for the 6.2 micron band of NO2
Probing topology by "heating": Quantized circular dichroism in ultracold atoms
We reveal an intriguing manifestation of topology, which appears in the
depletion rate of topological states of matter in response to an external
drive. This phenomenon is presented by analyzing the response of a generic 2D
Chern insulator subjected to a circular time-periodic perturbation: due to the
system's chiral nature, the depletion rate is shown to depend on the
orientation of the circular shake. Most importantly, taking the difference
between the rates obtained from two opposite orientations of the drive, and
integrating over a proper drive-frequency range, provides a direct measure of
the topological Chern number of the populated band (): this "differential
integrated rate" is directly related to the strength of the driving field
through the quantized coefficient . Contrary to the
integer quantum Hall effect, this quantized response is found to be non-linear
with respect to the strength of the driving field and it explicitly involves
inter-band transitions. We investigate the possibility of probing this
phenomenon in ultracold gases and highlight the crucial role played by edge
states in this effect. We extend our results to 3D lattices, establishing a
link between depletion rates and the non-linear photogalvanic effect predicted
for Weyl semimetals. The quantized circular dichroism revealed in this work
designates depletion-rate measurements as a universal probe for topological
order in quantum matter.Comment: 10 pages, 5 figures (including Sup. Mat.). Revised version, accepted
for publicatio
Valence Quark Distribution in A=3 Nuclei
We calculate the quark distribution function for 3He/3H in a relativistic
quark model of nuclear structure which adequately reproduces the nucleon
approximation, nuclear binding energies, and nuclear sizes for small nuclei.
The results show a clear distortion from the quark distribution function for
individual nucleons (EMC effect) arising dominantly from a combination of
recoil and quark tunneling effects. Antisymmetrization (Pauli) effects are
found to be small due to limited spatial overlaps. We compare our predictions
with a published parameterization of the nuclear valence quark distributions
and find significant agreement.Comment: 18pp., revtex4, 4 fig
Stratospheric constituent measurements using UV solar occultation technique
The photochemistry of the stratospheric ozone layer was studied as the result of predictions that trace amounts of pollutants can significantly affect the layer. One of the key species in the determination of the effects of these pollutants is the OH radical. A balloon flight was made to determine whether data on atmospheric OH could be obtained from lower resolution solar spectra obtained from high altitude during sunset
Evidence of Spatially Inhomogeous Pairing on the Insulating Side of a Disorder-Tuned Superconductor-Insulator Transition
Measurements of transport properties of amorphous insulating indium oxide
thin films have been interpreted as evidence of the presence of superconducting
islands on the insulating side of a disorder-tuned superconductor-insulator
transition. Although the films are not granular, the behavior is similar to
that observed in granular films. The results support theoretical models in
which the destruction of superconductivity by disorder produces spatially
inhomogenous pairing with a spectral gap.Comment: Revised title and content/argument. Totals: 4 pages, 3 figure
Kinetics of the helix-coil transition
Based on the Zimm-Bragg model we study cooperative helix-coil transition
driven by a finite-speed change of temperature. There is an asymmetry between
the coil-to-helix and helix-to-coil transition: the latter is displayed already
for finite speeds, and takes shorter time than the former. This hysteresis
effect has been observed experimentally, and it is explained here via
quantifying system's stability in the vicinity of the critical temperature. A
finite-speed cooling induces a non-equilibrium helical phase with the
correlation length larger than in equilibrium. In this phase the characteristic
length of the coiled domain and the non-equilibrium specific heat can display
an anomalous response to temperature changes. Several pertinent experimental
results on the kinetics helical biopolymers are discussed in detail.Comment: 6 pages, 8 figure
Color Magnetic Corrections to Quark Model Valence Distributions
We calculate order color magnetic corrections to the valence quark
distributions of the proton using the Los Alamos Model Potential wavefunctions.
The spin-spin interaction breaks the model SU(4) symmetry, providing a natural
mechanism for the difference between the up and down distributions. For a value
of sufficient to produce the mass splitting, we find up
and down quark distributions in reasonable agreement with experiment.Comment: 25 Pages, LA-UR-93-132
- …