358 research outputs found
On-line Excited-State Laser Spectroscopy of Trapped Short-Lived Ra Ions
As an important step towards an atomic parity violation experiment in one
single trapped Ra ion, laser spectroscopy experiments were performed with
on-line produced short-lived Ra ions. The isotope shift of
the 6\,^2D\,-\,7\,^2P and
6\,^2D\,-\,7\,^2P transitions and the hyperfine structure
constant of the 7\,^2S and 6\,^2D states in Ra
were measured. These values provide a benchmark for the required atomic theory.
A lower limit of ms for the lifetime of the metastable
6\,^2D state was measured by optical shelving.Comment: 4.2 pages, 6 figures, 2 tables
Isotope Shifts of the 6d\,^2D - 7p\,^2P Transition in Trapped Short-Lived Ra
Laser spectroscopy of short-lived radium isotopes in a linear Paul trap has
been performed. The isotope shifts of the 6d\,^2D -
7p\,^2P transition in Ra were measured, which are
sensitive to the short range part of the atomic wavefunctions. The results are
essential experimental input for improving the precision of atomic structure
calculation. This is indispensable for parity violation in Ra aiming at the
determination of the weak mixing angle.Comment: Accepted for publication in Physical Review A as a Rapid
Communicatio
Measurement of the half-life of the T= mirror decay of Ne and its implication on physics beyond the standard model
The superallowed mixed mirror decay
of Ne to F is excellently suited for high precision studies of
the weak interaction. However, there is some disagreement on the value of the
half-life. In a new measurement we have determined this quantity to be
= s, which differs
from the previous world average by 3 standard deviations. The impact of this
measurement on limits for physics beyond the standard model such as the
presence of tensor currents is discussed.Comment: 5 pages, 3 figures, 1 tabl
Development of a Neural Network Embedding for Quantifying Crack Pattern Similarity in Masonry Structures
The degree of similarity between damage patterns often correlates with the likelihood
of having similar damage causes. Therefore, deciding whether crack patterns are similar is one of
the key steps in assessing the conditions of masonry structures. To our knowledge, no literature has
been published regarding masonry crack pattern similarity measures that would correlate well
with assessment by structural engineers. Hence, currently, similarity assessments are solely
performed by experts and require considerable time and effort. Moreover, it is expensive, limited by
the availability of experts, and yields only qualitative answers. In this work, we propose an
automated approach that has the potential to overcome the above shortcomings and perform
comparably with experts. At its core is a deep neural network embedding that can be used to calculate a numerical distance between crack patterns on comparable façades. The embedding is
obtained from fitting a deep neural network to perform a classification task; i.e., to predict the crack
pattern archetype label from a crack pattern image. The network is fitted to synthetic crack patterns
simulated using a statistics-based approach proposed in this work. The simulation process can account for important crack pattern characteristics such as crack location, orientation, and length. The embedding transforms a crack pattern (raster image) into a 64-dimensional real-valued vector space where the closeness between two vectors is calculated as the cosine of their angle. The proposed approach is tested on 2D façades with and without openings, and with synthetic crack patterns that consist of a single crack and multiple cracks
Production of short lived radioactive beams of radium
Short lived Ra isotopes have been produced at the TRIP
facility in inverse kinematics via the fusion-evaporation reaction
Pb+C at 8 MeV/u. Isotopes are separated from other reaction
products online using the TRIP magnetic separator. The energetic radium
(Ra) isotopes at the exit of the separator were converted into low energy ions
with a thermal ionizer. Ra isotopes have been identified by observing their
decay and life times.Comment: 9 pages including 4 figures and 1 tabl
Development of a thermal ionizer as ion catcher
An effective ion catcher is an important part of a radioactive beam facility
that is based on in-flight production. The catcher stops fast radioactive
products and emits them as singly charged slow ions. Current ion catchers are
based on stopping in He and H gas. However, with increasing intensity of
the secondary beam the amount of ion-electron pairs created eventually prevents
the electromagnetic extraction of the radioactive ions from the gas cell. In
contrast, such limitations are not present in thermal ionizers used with the
ISOL production technique. Therefore, at least for alkaline and alkaline earth
elements, a thermal ionizer should then be preferred. An important use of the
TRIP facility will be for precision measurements using atom traps. Atom
trapping is particularly possible for alkaline and alkaline earth isotopes. The
facility can produce up to 10 s of various Na isotopes with the
in-flight method. Therefore, we have built and tested a thermal ionizer. An
overview of the operation, design, construction, and commissioning of the
thermal ionizer for TRIP will be presented along with first results for
Na and Na.Comment: 10 pages, 4 figures, XVth International Conference on Electromagnetic
Isotope Separators and Techniques Related to their Applications (EMIS 2007
The nature of the bonding in symmetrical pincer palladacycles
The accuracy of DFT-optimised geometries of the symmetrical pincer palladacycles PdNCN and PdSCS, [ClPd{2,6- Me2NCH2)2C6H3}] and [ClPd{2,6-(MeSCH2)2C6H3}] respectively, has been evaluated by investigating the performance of eight commonly used density functionals with four combinations of basis set, in reproducing their X-ray crystal structures. It was found that whilst the ωB97XD functional performed best over all, the PBE and TPSS functionals performed best when considering the palladium coordination geometry. The role of the donor atom in the stability and reactivity of the symmetric palladacycles, PdYCY, Y = N, S, or P, has been determined using Bader’s Atoms in Molecules method to elucidate the nature of the bonding, and using a model formation reaction, which involves the C–H activation of the pincer ligand YCY by PdCl2. The calculations reveal distinct differences in the bond strength and nature of the interaction of Pd with the donor atoms Y, which support differences in the thermodynamic stability of the palladacycles
On-line Excited-State Laser Spectroscopy of Trapped Short-Lived Ra Ions
As an important step towards an atomic parity violation experiment in one single trapped Ra ion, laser spectroscopy experiments were performed with on-line produced short-lived Ra ions. The isotope shift of the 6\,^2D\,-\,7\,^2P and 6\,^2D\,-\,7\,^2P transitions and the hyperfine structure constant of the 7\,^2S and 6\,^2D states in Ra were measured. These values provide a benchmark for the required atomic theory. A lower limit of ms for the lifetime of the metastable 6\,^2D state was measured by optical shelving
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