Search results for "ISOTOPE"

Resonance ionization spectroscopy for trace analysis and fundamental research

1994

Resonance ionization spectroscopy (RIS) and its combination with mass spectrometry (RIMS) have grown to become powerful techniques, which offer high sensitivity as well as elemental and isotopic selectivity. The principles of RIS and RIMS are introduced; they primarily concern the analysis of the optical spectra for the choice of efficient excitation schemes and the suitable design of the experimental apparatus. Recent applications span from studies of short-lived isotopes at on-line mass separators to a wide variety of trace analysis applications for radioactive isotopes, which can range from measurements of solar neutrino flux to environmental assessment.

Determination of U-Pb ages of zircons by direct measurement of the 210Pb/206Pb ratio

1993

Abstract Precise measurements of the 210Pb/206Pb ratio in zircons permits, for the first time, the determination of complete U-Pb ages by measurement of Pb isotopes only, without determination of the U-Pb ratio by isotope dilution. The 238U daughter isotope 210Pb is generally in radioactive equilibrium with 238U; however, the very short half-life of 210Pb (22.3a) results in extremely low 210Pb/206Pb ratios of ∼ 10−8, especially for Archaean zircons. These ratios have been determined using a Finnigan MAT 262® mass spectrometer equipped with a high abundance sensitivity lens system (RPQ). The accuracy of the 210Pb method has been tested on nine different zircon samples with 207Pb/206Pb ages f…

Sr and O isotope analyses reveal Late Cretaceous shark teeth in Iron Age strata of Jerusalem

2021

Quantum Effects on the Diffusivity of Hydrogen Isotopes in Zeolites

2019

The molecular sieving of H2 and its isotopes produced by nuclear plants is a long-standing research where some adsorption processes are well identified. However, some mechanisms governing the diffu...

The equilibrium structure and fundamental vibrational frequencies of dioxirane

1998

Complete sets of quadratic and cubic force constants calculated for four isotopomers of dioxirane (CH2OO) are used to estimate vibration-rotation interaction contributions to observed values of rotational constants (B″), thereby yielding empirical estimates of the corresponding equilibrium values (Be). At the highest levels of theory, least-squares refinements of atomic coordinates to both the empirical Be values and the associated isotope shifts yield consistent sets of structural parameters. Recommended values are re(CO)=1.3846±0.0005 A; re(OO)=1.5133±0.0005 A; re(CH)=1.0853±0.0015 A and θe(HCH)=117.03±0.20°. Semidiagonal quartic force constants (in the normal coordinate representation) a…

Investigation of diffusion and migration of hydrogen, deuterium and tritium in palladium in a Hall field

1991

Abstract The migration of hydrogen, deuterium and tritium in palladium in a Hall field at 343 K was investigated, using resistance and isotope methods. It was found that all isotopes of hydrogen migrate towards the negative Hall electrode. The effective charges of the migration in a Hall field are 194 ±3 e for hydrogen and 464± 5 e for deuterium and tritium. The results obtained confirm predictions of a tentative model based on the electron-balistic theories of migration in a Hall field.

High-resolution triple-resonance autoionization of uranium isotopes

2005

Abstract The near-threshold autoionization (AI) spectrum of uranium has been investigated by triple-resonance excitation with single-mode continuous lasers. Spectra were recorded over the first ∼30 cm − 1 above the first ionization limit at a resolution of 3 × 10 − 4 cm − 1 using intermediate states with different J values (6, 7, 8) to assign AI level total angular momentum J AI  = 5 to 9. Resonances with widths ranging from 8 MHz to 30 GHz were observed; the strongest ones have J AI  = 9 and widths of ∼60 MHz. Hyperfine structures for 235 U and isotope shifts for 234, 235 U have been measured in the two intermediate levels and in the final AI level for the most favorable excitation path. T…

Laser spectroscopy of neutron deficient lead and thallium isotopes: Systematics of nuclear radii in the Z = 82 region

1989

Publisher Summary The high sensitivity achievable in laser spectroscopic methods allows the extraction of nuclear quantities even of artificially produced short-lived nuclides far off from nuclear stability. By analyzing the hyperfine structure and the isotope shift magnetic dipole moments, the electric quadrupole moments and the change of the nuclear charge radius can be studied. This chapter describes an experiment that was carried out at the GSI on-line mass separator using collinear fast atomic-beam laser spectroscopy. Radioactive lead and thallium isotopes were produced by bombarding natural tungsten targets with oxygen beams. For the lighter thallium isotopes, a tantalum target was us…

Production of ionic and atomic beams of alkaline elements

1980

Abstract An on-line mass spectrometer has been developed and used to perform atomic and nuclear spectroscopy on long series of alkali isotopes including nuclei far from stability. The apparatus was on-line either to the ISOLDE mass separator or directly to the PS, proton beam. In the case of atomic spectroscopy, a thermal atomic beam is needed. As ISOLDE delivers 60 keV ions, a high efficiency “ion-to-atom coverter” has been developed. In all cases, an “ionizer” is required to produce 10 keV ions for the ion source of the mass spectrometer. These two special devices are described, their efficiency and the consequent delay times discussed. The different targets which have been developed for …

Triple Isotope Fractionation Exponents of Elements Measured by MC-ICP-MS—An Example of Mg

2019

In most chemical reactions, stable isotopes are fractionated in a mass-dependent manner, yielding correlated isotope ratios in elements with three or more stable isotopes. The proportionality between isotope ratios is set by the triple isotope fractionation exponent θ that can be determined precisely for, e.g., sulfur and oxygen by IRMS, but not for metal(loid) elements due to the lower precision of MC-ICP-MS analysis and smaller isotopic variations. Here, using Mg as a test case, we compute a complete metrologically robust uncertainty budget for apparent θ values and, with reference to this, present a new measurement approach that reduces uncertainty on θ values by 30%. T…