389 research outputs found
CARS spectroscopy of the () band in
Molecular hydrogen is a benchmark system for bound state quantum calculation
and tests of quantum electrodynamical effects. While spectroscopic measurements
on the stable species have progressively improved over the years, high
resolution studies on the radioactive isotopologues , and
have been limited. Here we present an accurate determination of
transition energies in the fundamental vibrational
band of the ground electronic state, by means of high resolution Coherent
Anti-Stokes Raman Spectroscopy. With the present experimental uncertainty of
, which is a fivefold improvement over previous
measurements, agreement with the latest theoretical calculations is
demonstrated.Comment: 9 pages, 3 figure
Relativistic and QED effects in the fundamental vibration of T
The hydrogen molecule has become a test ground for quantum electrodynamical
calculations in molecules. Expanding beyond studies on stable hydrogenic
species to the heavier radioactive tritium-bearing molecules, we report on a
measurement of the fundamental T vibrational splitting for rotational levels. Precision frequency metrology is performed
with high-resolution coherent anti-Stokes Raman spectroscopy at an experimental
uncertainty of ~MHz, where sub-Doppler saturation features are exploited
for the strongest transition. The achieved accuracy corresponds to a fifty-fold
improvement over a previous measurement, and allows for the extraction of
relativistic and QED contributions to T transition energies.Comment: 5 pages, 5 figure
Further evidence that imbalance of WT1 isoforms may be involved in Denys-Drash syndrome
No abstract availabl
Precision Measurement of Vibrational Quanta in Tritium Hydride (HT)
Saturated absorption measurements of transitions in the (2-0) band of
radioactive tritium hydride (HT) are performed with the ultra-sensitive
NICE-OHMS intracavity absorption technique in the range 1460-1510 nm. The
hyperfine structure of rovibrational transitions of HT, in contrast to that of
HD, exhibits a single isolated hyperfine component, allowing for the accurate
determination of hyperfineless rovibrational transition frequencies, resulting
in R(0) = (22) kHz and R(1) = (21)
kHz. This corresponds to an accuracy three orders of magnitude better than
previous measurements in tritiated hydrogen molecules. Observation of an
isolated component in P(1) with reversed signal amplitude contradicts models
for line shapes in HD based on cross-over resonances.Comment: 6 pages, 4 figures, Accepte
Sheared bioconvection in a horizontal tube
The recent interest in using microorganisms for biofuels is motivation enough
to study bioconvection and cell dispersion in tubes subject to imposed flow. To
optimize light and nutrient uptake, many microorganisms swim in directions
biased by environmental cues (e.g. phototaxis in algae and chemotaxis in
bacteria). Such taxes inevitably lead to accumulations of cells, which, as many
microorganisms have a density different to the fluid, can induce hydrodynamic
instabilites. The large-scale fluid flow and spectacular patterns that arise
are termed bioconvection. However, the extent to which bioconvection is
affected or suppressed by an imposed fluid flow, and how bioconvection
influences the mean flow profile and cell transport are open questions. This
experimental study is the first to address these issues by quantifying the
patterns due to suspensions of the gravitactic and gyrotactic green
biflagellate alga Chlamydomonas in horizontal tubes subject to an imposed flow.
With no flow, the dependence of the dominant pattern wavelength at pattern
onset on cell concentration is established for three different tube diameters.
For small imposed flows, the vertical plumes of cells are observed merely to
bow in the direction of flow. For sufficiently high flow rates, the plumes
progressively fragment into piecewise linear diagonal plumes, unexpectedly
inclined at constant angles and translating at fixed speeds. The pattern
wavelength generally grows with flow rate, with transitions at critical rates
that depend on concentration. Even at high imposed flow rates, bioconvection is
not wholly suppressed and perturbs the flow field.Comment: 19 pages, 9 figures, published version available at
http://iopscience.iop.org/1478-3975/7/4/04600
Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment
The KATRIN experiment aims at the direct model-independent determination of
the average electron neutrino mass via the measurement of the endpoint region
of the tritium beta decay spectrum. The electron spectrometer of the MAC-E
filter type is used, requiring very high stability of the electric filtering
potential. This work proves the feasibility of implanted 83Rb/83mKr calibration
electron sources which will be utilised in the additional monitor spectrometer
sharing the high voltage with the main spectrometer of KATRIN. The source
employs conversion electrons of 83mKr which is continuously generated by 83Rb.
The K-32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7
eV) is shown to fulfill the KATRIN requirement of the relative energy stability
of +/-1.6 ppm/month. The sources will serve as a standard tool for continuous
monitoring of KATRIN's energy scale stability with sub-ppm precision. They may
also be used in other applications where the precise conversion lines can be
separated from the low energy spectrum caused by the electron inelastic
scattering in the substrate.Comment: 30 pages, 10 figures, 1 table, minor revision of the preprint,
accepted by JINST on 5.2.201
Precision measurement of the fundamental vibrational frequencies of tritium-bearing hydrogen molecules: T, DT, HT
High-resolution coherent Raman spectroscopic measurements of all three
tritium-containing molecular hydrogen isotopologues T, DT and HT were
performed to determine the ground electronic state fundamental Q-branch () transition frequencies at accuracies of
cm. An over hundred-fold improvement in accuracy over previous
experiments allows the comparison with the latest ab initio calculations in the
framework of Non-Adiabatic Perturbation Theory including nonrelativisitic,
relativisitic and QED contributions. Excellent agreement is found between
experiment and theory, thus providing a verification of the validity of the
NAPT-framework for these tritiated species. While the transition frequencies
were corrected for ac-Stark shifts, the contributions of non-resonant
background as well as quantum interference effects between resonant features in
the nonlinear spectroscopy were quantitatively investigated, also leading to
corrections to the transition frequencies. Methods of saturated CARS with the
observation of Lamb dips, as well as the use of continuous-wave radiation for
the Stokes frequency were explored, that might pave the way for future
higher-accuracy CARS measurements.Comment: 15 pages, 13 figure
Precision tests of nonadiabatic perturbation theory with measurements on the DT molecule
First-principles calculations are presented for fundamental vibrational splitting energies of tritium-bearing molecular hydrogen species with the improved treatment of the nonrelativistic, relativistic, and quantum electrodynamic energy contributions resulting in a total uncertainty of 0.00011Â cm^{â1} for DT, or about a 100-times improvement over previous results. Precision coherent Raman spectroscopic measurements of Q(J=0â5) transitions in DT were performed at an accuracy of <0.0004Â cm^{â1}, representing an even larger 250-fold improvement over previous experiments. Perfect agreement between experiment and theory is found, within 1Ï, for all six transitions studied
Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy
The gas circulation loop LOOPINO has been set up and commissioned at Tritium
Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium
mixtures under conditions similar to the inner loop system of the neutrino-mass
experiment KATRIN, which is currently under construction. A custom-made
interface is used to connect the tritium containing measurement cell, located
inside a glove box, with the Raman setup standing on the outside. A tritium
sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more
than three weeks with a total throughput of 770 g of tritium. Compositional
changes in the sample and the formation of tritiated and deuterated methanes
CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen
isotope exchange reactions and gas-wall interactions, due to tritium {\beta}
decay. A precision of 0.1% was achieved for the monitoring of the T_2
Q_1-branch, which fulfills the requirements for the KATRIN experiment and
demonstrates the feasibility of high-precision Raman measurements with tritium
inside a glove box
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