Search results for "DIPOLE"
showing 10 items of 982 documents
Nile Basin Climates
2009
The climate of the Nile Basin is characterised by a strong latitudinal wetness gradient. Whereas the areas north of 18°N remain dry most of the year, to the south there is a gradual increase of monsoon precipitation amounts. Rainfall regimes can be divided into 9 types, among which summer peak regimes dominate. In the southern half of the basin, mesoscale circulation features and associated contrasts in local precipitation patterns develop as a result of a complex interplay involving topography, lakes and swamps. Precipitation changes and variability show up as 3 distinct modes of variability. Drying trends since the 1950s are found in central Sudan and to some extent the Ethiopian Highland…
Two hybrid organometallic-inorganic layered magnets from the series [ ZIIICp*2] [ MIIMIII(ox)3] studied with μ+SR
2004
We present zero-field muon spin relaxation (ZF-μ + SR) measurements on two examples of a new series of hybrid organometallic-inorganic layered magnets, namely ferromagnetic [FeCp* 2 ][MnCr(ox) 3 ] and ferrimagnetic [CoCp* 2 ][FeFe(ox) 3 ] (where ox = oxalate and Cp* = pentame- thyl-cyclopentadienyl). Both materials show multi-component muon spin precession signals characteristic of quasistatic magnetic fields at several distinct muon sites. The temperature dependence of the precession frequencies allow critical exponents to be extracted. Possible muon sites are discussed on the basis of dipole field calculations.
Probing Surface Quantum Flows in Deformed Pygmy Dipole Modes
2017
In order to explore the nature of collective modes in weakly bound nuclei, we have investigated deformation effects and surface flow patterns of isovector dipole modes in a shape-coexisting nucleus $^{40}$Mg. The calculations were done in a fully self-consistent continuum finite-amplitude Quasiparticle Random Phase Approximation (QRPA) in a large deformed spatial mesh. An unexpected result of pygmy and giant dipole modes having disproportionate deformation splittings in strength functions was obtained. Furthermore, the transition current densities demonstrate that the long-sought core-halo oscillation in pygmy resonances is collective and compressional, corresponding to the lowest excitatio…
Molecular polarizability of Si/Ge/GaAs semiconductors clusters
2004
The interacting induced dipole polarization model implemented in our program for the calculation of molecular polarizabilities (POLAR) is used for the calculation of the molecular dipole-dipole polarizability ${\overline{\overline{α}}}$. POLAR is tested with Si$_{n}$, Ge$_{n}$ and Ga$_{n}$As$_{m}$ small clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are in agreement with reference calculations performed with our version of the program PAPID (polarisabilites atomiques par interactions dipolaires) and with reference computations from Dr. J.R. Che…
Theory of Neutrinos: A White Paper
2005
During 2004, four divisions of the American Physical Society commissioned a study of neutrino physics to take stock of where the field is at the moment and where it is going in the near and far future. Several working groups looked at various aspects of this vast field. The summary was published as a main report entitled ``The Neutrino Matrix'' accompanied by short 50 page versions of the report of each working group. Theoretical research in this field has been quite extensive and touches many areas and the short 50 page report provided only a brief summary and overview of few of the important points. The theory discussion group felt that it may be of value to the community to publish the e…
Testing isotropy of the universe using the Ramsey resonance technique on ultracold neutron spins
2010
Physics at the Planck scale could be revealed by looking for tiny violations of fundamental symmetries in low energy experiments. In 2008, a sensitive test of the isotropy of the Universe using has been performed with stored ultracold neutrons (UCN), this is the first clock-comparison experiment performed with free neutrons. During several days we monitored the Larmor frequency of neutron spins in a weak magnetic field using the Ramsey resonance technique. An non-zero cosmic axial field, violating rotational symmetry, would induce a daily variation of the precession frequency. Our null result constitutes one of the most stringent tests of Lorentz invariance to date.
Statistical sensitivity of the nEDM apparatus at PSI to n − n′ oscillations
2018
The neutron and its hypothetical mirror counterpart, a sterile state degenerate in mass, could spontaneously mix in a process much faster than the neutron β-decay. Two groups have performed a series of experiments in search of neutron – mirror-neutron (n − n′) oscillations. They reported no evidence, thereby setting stringent limits on the oscillation time τnn′. Later, these data sets have been further analyzed by Berezhiani et al.(2009–2017), and signals, compatible with n − n′ oscillations in the presence of mirror magnetic fields, have been reported. The Neutron Electric Dipole Moment Collaboration based at the Paul Scherrer Institute performed a new series of experiments to further test…
Neutron powder diffraction study in the mixed molecular system (NaCN)1−x(KCN)x
1989
A detailed structural analysis of (NaCN${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$(KCN${)}_{\mathrm{x}}$ mixed crystals with x=0.02, 0.19, and 0.95 was performed by neutron powder diffraction. The structural parameters of the cubic phases were refined, applying a model of preferred orientations. Different noncubic low-temperature phases were observed for x=0.02 and 0.95. For x=0.02 the antiferroelectric ordering of ${\mathrm{CN}}^{\mathrm{\ensuremath{-}}}$ dipoles at low temperatures is accompanied by significant alkali-alkali and alkali-${\mathrm{CN}}^{\mathrm{\ensuremath{-}}}$ sublattice shifts. Structural data are presented together with previous results for mixed crystals with x=0.59 and…
The n2EDM experiment at the Paul Scherrer Institute
2018
We present the new spectrometer for the neutron electric dipole moment (nEDM) search at the Paul Scherrer Institute (PSI), called n2EDM. The setup is at room temperature in vacuum using ultracold neutrons. n2EDM features a large UCN double storage chamber design with neutron transport adapted to the PSI UCN source. The design builds on experience gained from the previous apparatus operated at PSI until 2017. An order of magnitude increase in sensitivity is calculated for the new baseline setup based on scalable results from the previous apparatus, and the UCN source performance achieved in 2016.
Disentangling decaying isomers and searching for signatures of collective excitations in β decay
2019
6 pags., 3 figs., 1 tab. -- 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK