408 research outputs found
Collisional properties of cold spin-polarized nitrogen gas: theory, experiment, and prospects as a sympathetic coolant for trapped atoms and molecules
We report a combined experimental and theoretical study of collision-induced
dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use
buffer gas cooling to create trapped samples of 14N and 15N atoms with
densities 5+/-2 x 10^{12} cm-3 and measure their magnetic relaxation rates at
milli-Kelvin temperatures. Rigorous quantum scattering calculations based on
accurate ab initio interaction potentials for the 7Sigma_u electronic state of
N2 demonstrate that dipolar relaxation in N + N collisions occurs at a slow
rate of ~10^{-13} cm3/s over a wide range of temperatures (1 mK to 1 K) and
magnetic fields (10 mT to 2 T). The calculated dipolar relaxation rates are
insensitive to small variations of the interaction potential and to the
magnitude of the spin-exchange interaction, enabling the accurate calibration
of the measured N atom density. We find consistency between the calculated and
experimentally determined rates. Our results suggest that N atoms are promising
candidates for future experiments on sympathetic cooling of molecules.Comment: 48 pages, 17 figures, 3 table
Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment
In the PS209 experiments at CERN two kinds of measurements were performed:
the in-beam measurement of X-rays from antiprotonic atoms and the
radiochemical, off-line determination of the yield of annihilation products
with mass number A_t -1 (less by 1 than the target mass). Both methods give
observables which allows to study the peripheral matter density composition and
distribution.Comment: LaTeX (espcrc1 style), 6 pages, 3 EPS figures, 1 table, Proceedings
of the Sixth Biennal Conference on Low-Energy Antiproton Physics LEAP 2000,
Venice, Ital
Neutron density distributions from antiprotonic 208Pb and 209Bi atoms
The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi.
Widths and shifts of the levels due to the strong interaction were determined.
Using modern antiproton-nucleus optical potentials the neutron densities in the
nuclear periphery were deduced. Assuming two parameter Fermi distributions
(2pF) describing the proton and neutron densities the neutron rms radii were
deduced for both nuclei. The difference of neutron and proton rms radii /\r_np
equal to 0.16 +-(0.02)_{stat} +- (0.04)_{syst} fm for 208Pb and 0.14 +-
(0.04)_{stat} +- (0.04)_{syst} fm for 209Bi were determined and the assigned
systematic errors are discussed. The /\r_np values and the deduced shapes of
the neutron distributions are compared with mean field model calculations.Comment: 22 pages, 8 tables, 15 figure
Strong interaction and E2 effect in even- A antiprotonic Te atoms
The x-ray cascade from antiprotonic atoms was studied for Te-122, Te-124, Te-126, Te-128, and Te-130. Widths and shifts due to the strong interaction were deduced for several levels. The E2 nuclear resonance effect was observed in all investigated nuclei. In Te-130 the E2 resonance allowed to determine level widths and shifts of the LS-split deeply bound (n,l)=(6,5) state, otherwise unobservable. The measured level widths and shifts, corrected for the E2-resonance effect, were used to investigate the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with results of the previously introduced radiochemical method and with Hartree-Fock-Bogoliubov model calculations
Study on homogenization of synthetic GNSS-Retrieved IWV time series and its impact on trend estimates with autoregressive noise
Póster presentado en: EGU General Assembly celebrada del 23 al 28 de abril de 2017 en Viena, Austria.A synthetic benchmark dataset of Integrated Water Vapour (IWV) was created within the activity of “Data homogenisation” of sub-working group WG3 of COST ES1206 Action. The benchmark dataset was created basing on the analysis of IWV differences retrieved by Global Positioning System (GPS) International GNSS Service (IGS) stations using European Centre for Medium-Range Weather Forecats (ECMWF) reanalysis data (ERA-Interim). Having analysed a set of 120 series of IWV differences (ERAI-GPS) derived for IGS stations, we delivered parameters of a number of gaps and breaks for every certain station. Moreover, we estimated values of trends, significant seasonalities and character of residuals when deterministic model was removed. We tested five different noise models and found that a combination of white and autoregressive processes of first order describes the stochastic part with a good accuracy. Basing on this analysis, we performed Monte Carlo simulations of 25 years long data with two different types of noise: white as well as combination of white and autoregressive processes. We also added few strictly defined offsets, creating three variants of synthetic dataset: easy, less complicated and fully complicated. The synthetic dataset we present was used as a benchmark to test various statistical tools in terms of homogenisation task. In this research, we assess the impact of the noise model, trend and gaps on the performance of statistical methods to detect simulated change points
Performance of various homogenization tools on a synthetic benchmark dataset of GPS and ERA-interim IWV differences
Presentación realizada en: IAG-IASPEI 39th Joint Scientific Assembly celebrada en Kobe, Japón, del 30 de julio al 4 de agosto de 2017
Adaptive mechanism design and game theoretic analysis of auction-driven dynamic spectrum access in cognitive radio networks
Homogenizing GPS integrated water vapour time series: methodology and benchmarking the algorithms on synthetic datasets
We would like to thank the COST Action ES1206 GNSS4SWEC for financial support
Nucleon density in the nuclear periphery determined with antiprotonic x-rays: cadmium and tin isotopes
The x-ray cascade from antiprotonic atoms was studied for 106Cd, 116Cd,
112Sn, 116Sn, 120Sn, and 124Sn. Widths and shifts of the levels due to strong
interaction were deduced. Isotopic effects in the Cd and Sn isotopes are
clearly seen. The results are used to investigate the nucleon density in the
nuclear periphery. The deduced neutron distributions are compared with the
results of the previously introduced radiochemical method and with HFB
calculations
Nucleon density in the nuclear periphery determined with antiprotonic x rays: Calcium isotopes
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