The Experts below are selected from a list of 2388 Experts worldwide ranked by ideXlab platform
Klaus Blaum - One of the best experts on this subject based on the ideXlab platform.
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penning trap Mass measurements of the deuteron and the hd molecular ion
Nature, 2020Co-Authors: S Rau, F Heise, Florian Kohlerlanges, Sangeetha Sasidharan, Raphael Haas, D Renisch, Christoph E Dullmann, W Quint, Sven Sturm, Klaus BlaumAbstract:The Masses of the lightest Atomic nuclei and the electron Mass1 are interlinked, and their values affect observables in Atomic2, molecular3–5 and neutrino physics6, as well as metrology. The most precise values for these fundamental parameters come from Penning trap Mass spectrometry, which achieves relative Mass uncertainties of the order of 10−11. However, redundancy checks using data from different experiments reveal considerable inconsistencies in the Masses of the proton, the deuteron and the helion (the nucleus of helium-3), suggesting that the uncertainty of these values may have been underestimated. Here we present results from absolute Mass measurements of the deuteron and the HD+ molecular ion using 12C as a Mass reference. Our value for the deuteron Mass, 2.013553212535(17) Atomic Mass Units, has better precision than the CODATA value7 by a factor of 2.4 and differs from it by 4.8 standard deviations. With a relative uncertainty of eight parts per trillion, this is the most precise Mass value measured directly in Atomic Mass Units. Furthermore, our measurement of the Mass of the HD+ molecular ion, 3.021378241561(61) Atomic Mass Units, not only allows a rigorous consistency check of our results for the Masses of the deuteron (this work) and the proton8, but also establishes an additional link for the Masses of tritium9 and helium-3 (ref. 10) to the Atomic Mass Unit. Combined with a recent measurement of the deuteron-to-proton Mass ratio11, the uncertainty of the reference value of the proton Mass7 can be reduced by a factor of three. Penning trap Mass spectrometry is used to measure the Masses of the deuteron and the HD+ ion with unprecedented precision, reducing the uncertainty of the proton Mass reference value.
J Musser - One of the best experts on this subject based on the ideXlab platform.
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measurement of the isotopic composition of cosmic ray helium lithium beryllium and boron up to 1700 mev per Atomic Mass Unit
The Astrophysical Journal, 2000Co-Authors: S P Ahlen, N Greene, D Loomba, J W Mitchell, C Bower, R Heinz, S Mufson, J MusserAbstract:We present data from the second flight of the superconducting magnet instrument for light isotopes (SMILI), which took place on 1991 July 24. This instrument was optimized to determine the isotopic composition of He, Li, Be, and B in the Galactic cosmic rays, up to an energy of 2 GeV amu-1. The abundances of He, Li, and B are found to be consistent with standard models of cosmic-ray propagation. Our measurement of the abundances of the beryllium isotopes suggests an enhancement of the fraction of the isotope 10Be over that found at low energy. Of 26 beryllium events, nine are found to be 10Be. Monte Carlo calculations based on this observation imply the mean lifetime of cosmic rays to be less than 6 Myr at the 97.5% confidence level.
N Greene - One of the best experts on this subject based on the ideXlab platform.
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measurement of the isotopic composition of cosmic ray helium lithium beryllium and boron up to 1700 mev per Atomic Mass Unit
The Astrophysical Journal, 2000Co-Authors: S P Ahlen, N Greene, D Loomba, J W Mitchell, C Bower, R Heinz, S Mufson, J MusserAbstract:We present data from the second flight of the superconducting magnet instrument for light isotopes (SMILI), which took place on 1991 July 24. This instrument was optimized to determine the isotopic composition of He, Li, Be, and B in the Galactic cosmic rays, up to an energy of 2 GeV amu-1. The abundances of He, Li, and B are found to be consistent with standard models of cosmic-ray propagation. Our measurement of the abundances of the beryllium isotopes suggests an enhancement of the fraction of the isotope 10Be over that found at low energy. Of 26 beryllium events, nine are found to be 10Be. Monte Carlo calculations based on this observation imply the mean lifetime of cosmic rays to be less than 6 Myr at the 97.5% confidence level.
D Loomba - One of the best experts on this subject based on the ideXlab platform.
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measurement of the isotopic composition of cosmic ray helium lithium beryllium and boron up to 1700 mev per Atomic Mass Unit
The Astrophysical Journal, 2000Co-Authors: S P Ahlen, N Greene, D Loomba, J W Mitchell, C Bower, R Heinz, S Mufson, J MusserAbstract:We present data from the second flight of the superconducting magnet instrument for light isotopes (SMILI), which took place on 1991 July 24. This instrument was optimized to determine the isotopic composition of He, Li, Be, and B in the Galactic cosmic rays, up to an energy of 2 GeV amu-1. The abundances of He, Li, and B are found to be consistent with standard models of cosmic-ray propagation. Our measurement of the abundances of the beryllium isotopes suggests an enhancement of the fraction of the isotope 10Be over that found at low energy. Of 26 beryllium events, nine are found to be 10Be. Monte Carlo calculations based on this observation imply the mean lifetime of cosmic rays to be less than 6 Myr at the 97.5% confidence level.
François Robert - One of the best experts on this subject based on the ideXlab platform.
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Archean kerogen as a new tracer of atmospheric evolution: Implications for dating the widespread nature of early life.
Science advances, 2018Co-Authors: David V. Bekaert, Frédéric Delarue, François Robert, Michael W. Broadley, Guillaume Avice, Bernard MartyAbstract:Understanding the composition of the Archean atmosphere is vital for unraveling the origin of volatiles and the environmental conditions that led to the development of life. The isotopic composition of xenon in the Archean atmosphere has evolved through time by Mass-dependent fractionation from a precursor comprising cometary and solar/chondritic contributions (referred to as U-Xe). Evaluating the composition of the Archean atmosphere is challenging because limited amounts of atmospheric gas are trapped within minerals during their formation. We show that organic matter, known to be efficient at preserving large quantities of noble gases, can be used as a new archive of atmospheric noble gases. Xe isotopes in a kerogen isolated from the 3.0–billion-year–old Farrel Quartzite (Pilbara Craton, Western Australia) are Mass fractionated by 9.8 ± 2.1 per mil (‰) (2σ) per Atomic Mass Unit, in line with a progressive evolution toward modern atmospheric values. Archean atmospheric Xe signatures in kerogens open a new avenue for following the evolution of atmospheric composition through time. The degree of Mass fractionation of Xe isotopes relative to the modern atmosphere can provide a time stamp for dating Archean kerogens and therefore narrowing the time window for the diversification of early life during the Archean eon.
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adsorption of xenon ions onto defects in organic surfaces implications for the origin and the nature of organics in primitive meteorites
Geochimica et Cosmochimica Acta, 2011Co-Authors: Yves Marrocchi, Bernard Marty, Peter Reinhardt, François RobertAbstract:Noble gases trapped in primitive meteorites are quantitatively hosted by a poorly defined organic phase, labeled phase Q. Xenon is enriched in heavy isotopes by +1.30 ± 0.06% per Atomic Mass Unit (amu, 1r) in phase Q relative to solar. To understand the origin of this fractionation, we have performed adsorption experiments of xenon atoms and ions, ionized in a radiofrequency plasma. Within the reaction vessel, anthracite was heated and the resulting smoke deposited onto the walls of the vessel, resulting in carbon-rich films. Xenon was trapped in the carbon films either as ions in the ionization zone of the vessel, or as neutral atoms outside this zone. Xenon trapped as ionic Xe is tightly bound and is enriched by +1.36 ± 0.05%/amu (1r) in heavy isotopes, reproducing the isotopic fractionation of xenon trapped in phase Q relative to solar. Neutral xenon is more loosely trapped, is in much lower concentration, and is not isotopically fractionated. Ionized conditions allow the constant xenon isotopic composition observed in meteorite during stepwise heating release to be reproduced. Furthermore, the trapping efficiency of Xe + estimated from these experiments is consistent with the high xenon concentration measured in phase Q of primitives meteorites. Xenon was not trapped in the film by implantation because the energies of the incident Xe atoms and ions were far too low (<1 eV). From the difference of behavior between ionic and neutral forms, we propose that xenon ions were trapped via chemical bonding at the surface of the newly created C-rich film. The observed Mass-dependent fractionation of xenon is unlikely to have occurred in the gas phase. It is more probably related to variations in chemical bonding strengths of Xe isotopes as chemical bonds involving heavy Xe isotopes are more stable than those involving light ones. For young stars, including the young Sun, photons emitted in the far UV energy range able to ionize noble gases (<100 nm) were orders of magnitude more abundant than for the Present-day Sun, allowing efficient ionization of gaseous species. A way to achieve Q-noble gas fractionation and trapping was UV irradiation by nearby young stars from O/B association of the surface of growing organic grains in the outer part of the solar system or by the young Sun at the edge of the disk. 2011 Elsevier Ltd. All rights reserved.