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[en] The first investigation of isotope shifts in both the atomic and ionic resonance lines of radium has been carried out using the technique of on-line collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN. The measurements cover 19 isotopes in the mass range 208 ≤ A ≤ 232 with half-lives between 23 ms and 1600 y. The differences in the nuclear mean square charge radii δ(r2) have been evaluated and - together with earlier published spins and moments from the hyperfine structure - related to nuclear deformation. In particular the inversion of the odd-even staggering effect for the isotopes 221Ra, 223Ra and 225Ra can be interpreted by the presence of octupole instability and adds weight to the concept of near-stable octupole deformation in the odd-A isotopes which already explained their spins and magnetic moments. (orig.)
[en] Radium ion is an ideal candidate for high precision experiments. Atomic Parity Non-Conservation (APNC) can be measured in a single trapped Ra+. This enables a precise measurement of the electroweak mixing angle (Weinberg angle) in the Standard Model of particle physics at the lowest possible momentum transfer. Ultra-narrow transitions in this system can also be exploited to realize a high stability frequency standard. As an important step towards such high precision experiments, excited-state laser spectroscopy has been performed with trapped short-lived 209-214Ra+ ions. The results on hyperfine structures, isotope shifts and lifetimes are important input for the required atomic theory, the precision of which is indispensable to extract the Weinberg angle. The experimental set up for laser cooling and trapping a single radium ion is underway.
[en] An α-spectrometric method for the rapid determination of radium isotopes (223Ra, 224Ra and 226Ra) in environmental samples is presented. Using EmporeTM Radium Rad Disks complete separation of the target radionuclides is achieved. The high selectivity of these Rad Disks allows the straightforward use of 225Ra as yield tracer. Chemical yield is up to 92±9%. The chemical procedure can be accomplished within 5 h. α-Sources show energy resolution in the range of typically 26-40 keV (FWHM). Despite minimal thickness of the sources no significant radon (Rn) losses can be observed
[en] A precision measurement of atomic parity violation in order to determine electroweak mixing angle at low energy scale is underway at the KVI, University of Groningen. The experiment exploits the large sensitivity of a single trapped Ra+ ion. It requires the trapping of short lived radium ions in a Paul trap. Our first laser spectroscopy on an ensemble of trapped short-lived 209-214Ra+ isotopes employed buffer gas cooled ions in a linear Paul trap. It provided hyperfine structure of the 6d 2D3/2 states and isotope shift of the 6d 2D3/2-7p 2P1/2 transition. In a next step the buffer gas cooled Ra ions are extracted from the trap and transported in an electrostatic transport system towards a small Paul trap in an UHV environment. Here the ion can be cooled and subsequently microwave transitions between hyperfine states in the 6d 2D3/2 manifold can be driven in order to yield high precision results on the hyperfine constants. These results provide input for the ongoing precision atomic structure calculations.
[en] The first investigation of hyperfine structure in radium isotopes has enabled the determination of nuclear spins, magnetic dipole and electric quadrupole moments of the isotopes with mass numbers A=211, 213, 221, 223, 225, 227 and 229. Isotope shifts in the mass range A=208-232 have also been measured. These studies were carried out using the technique of on-line collinear fast beam laser spectroscopy. (orig.)
[en] Radium isotopes are widely used in marine studies (eg. to trace water masses, to quantify mixing processes or to study submarine groundwater discharge). While 228Ra and 226Ra are usually measured using gamma spectrometry, short-lived Ra isotopes (224Ra and 223Ra) are usually measured using a Radium Delayed Coincidence Counter (RaDeCC). Here we show that the four radium isotopes can be analyzed using gamma spectrometry. We report 226Ra, 228Ra, 224Ra, 223Ra activities measured using low-background gamma spectrometry in standard samples, in water samples collected in the vicinity of our laboratory (La Palme and Vaccares lagoons, France) but also in seawater samples collected in the plume of the Amazon river, off French Guyana (AMANDES project). The 223Ra and 224Ra activities determined in these samples using gamma spectrometry were compared to the activities determined using RaDeCC. Activities determined using the two techniques are in good agreement. Uncertainties associated with the 224Ra activities are similar for the two techniques. RaDeCC is more sensitive for the detection of low 223Ra activities. Gamma spectrometry thus constitutes an alternate method for the determination of short-lived Ra isotopes.
[en] Modified macroscopic-microscopic calculations of the potential energy of nuclei in the Ra-Th region are performed. A stable octupole deformation of the nuclei is obtained. The lowest Kπ = 0- states are interpreted as being associated with this deformation. (orig.)
[en] Four isotopes of radium with different half-lives exist in nature. In aquatic systems, radium isotopes present distinct characteristics in salt water and fresh water environments. In fresh waters, radium appears adsorbed to particulate material while in sea water radium presents a conservative behavior, being the concentration of different isotopes of radium governed by the processes of dilution, advection and diffusion, as well as radioactive decay. The four natural isotopes of radium are tracers extensively used to determine ratios of water mixture and to calculate the period since the radium was added to the water column. The short-lived isotopes, 223Ra (half-life = 11.4 days) and 224Ra (half-life = 3.66 days), are continually regenerated from decay of their thorium parents, which are perpetually bound to particles surfaces. On the other hand, the long-lived isotopes, 226Ra (half-life = 1600 yrs) and 228Ra (half-life = 5.7 yrs), require considerable time for regeneration. These fluxes must be sustained by input water from rivers, sediments, SGD, or other sources. In the present work, developed at the estuary of the Paraiba do Sul River, the short half-lived radium isotopes (224Ra and 223Ra) were determined using the technique of coincidence delayed developed. The isotopes of long half-lifed (2226Ra and 2228Ra) were determined by the technique of total alpha and beta counting, after the dissolution of the MnO2 fiber used to pre-concentrate radium. (author)
[en] The enthalpy, Gibbs free energy, and entropies of aqueous radium species and radium solids have been evaluated from empirical data, or estimated when necessary for 25 deg C and 1 bar. Estimates were based on such approaches as extrapolation of the thermodynamic properties of Ca, Sr, and Ba complexes and solids plotted against cationic radii and charge to radius functions, and the use of the Fuoss or electrostatic mathematical models of ion pair formation. Resultant log K (assoc) and ΔH0 (assoc) (kcal/mol) values are given for RaOH+; RaCl+; RaCO30; and RaSO40. Log Ksp and ΔH0 (dissoc) (kcal/mol) values are given for RaCO3(c) and RaSO4(c). Trace Ra solid solution in salts of Pb and of the lighter alkaline earths, has been appraised based on published distribution coefficient (D) data. The empirical solid solution data have been used to derive both enthalpies and Gibbs free energies of solid solution of trace Ra in sulfate and carbonate minerals up to 100 deg C. Results show that in every case D values decrease with increasing temperature. Among the sulfate and carbonate minerals, D values decrease for the following minerals in the order: anhydride > celestite > anglesite > barite > aragonite > strontianite > witherite > cerussite. (author)
[en] The radioactivity of more than 500 samples of groundwater from locations throughout Australia was measured. Some samples contained radium at levels of up to 10 times higher than the water in uranium tailings dams. A scheme that indicates the chance of finding uranium, based on the analysis of a groundwater sample, was developed which should help uranium prospectors locate new deposits