Dielectronic Resonance Method for Measuring Isotope Shifts

Longstanding problems in the comparison of very accurate hyperfine-shift measurements to theory were partly overcome by precise measurements on few-electron highly-charged ions. Still the agreement between theory and experiment is unsatisfactory. In this paper, we present a radically new way of precisely measuring hyperfine shifts, and demonstrate its effectiveness in the case of the hyperfine shift of $4s\_{1/2}$ and $4p\_{1/2}$ in $^{207}\mathrm{Pb}^{53+}$. It is based on the precise detection of dielectronic resonances that occur in electron-ion recombination at very low energy. This allows us to determine the hyperfine constant to around 0.6 meV accuracy which is on the order of 10%

High-precision measurements of krypton and xenon isotopes with a new static-mode quadrupole ion trap mass spectrometer

Measuring the abundance and isotopic composition of noble gases in planetary atmospheres can answer fundamental questions in cosmochemistry and comparative planetology. However, noble gases are rare elements, a feature making their measurement challenging even on Earth. Furthermore, in space applications, power consumption, volume and mass constraints on spacecraft instrument accommodations require the development of compact innovative instruments able to meet the engineering requirements of the mission while still meeting the science requirements. Here we demonstrate the ability of the quadrupole ion trap mass spectrometer (QITMS) developed at the Jet Propulsion Laboratory (Caltech, Pasadena) to measure low quantities of heavy noble gases (Kr, Xe) in static operating mode and in the absence of a buffer gas such as helium. The sensitivity reaches 10^(13) cps Torr^(−1) (about 10^(11) cps Pa^(−1)) of gas (Kr or Xe). The instrument is able to measure gas in static mode for extended periods of time (up to 48 h) enabling the acquisition of thousands of isotope ratios per measurement. Errors on isotope ratios follow predictions of the counting statistics and the instrument provides reproducible results over several days of measurements. For example, 1.7 × 10^(−10) Torr (2.3 × 10^(−8) Pa) of Kr measured continuously for 7 hours yielded a 0.6‰ precision on the ^(86)Kr/^(84)Kr ratio. Measurements of terrestrial and extraterrestrial samples reproduce values from the literature. A compact instrument based upon the QITMS design would have a sensitivity high enough to reach the precision on isotope ratios (e.g. better than 1% for ^(129,131–136)Xe/^(130)Xe ratios) necessary for a scientific payload measuring noble gases collected in the Venus atmosphere

SEIS: Insight’s Seismic Experiment for Internal Structure of Mars

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars’ surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking’s Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars’ surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of Mw ∼ 3 at 40◦ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution

Electron-ion recombination of Be-like C, N, and O

The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of N3+ and O4+. Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of O4+, the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures

High-precision measurements of krypton and xenon isotopes with a new static-mode quadrupole ion trap mass spectrometer

International audienceA quadrupole ion trap mass spectrometer measures precisely the abundance and isotopic composition of small amounts of noble gases

In-Situ Exploration of the Exoplanet Next Door: Revealing the Chemistry, Habitability and Evidence of Biological Processes in the Clouds of Venus

International audienceWith its thick CO_2 atmosphere, moonless skies, and proximity to the Sun, Venus is considered to be a close analog to common, presumably lifeless, rocky exoplanets. However, the recent suggestion of PH_3 in the clouds of Venus (Greaves et al., 2020) has sparked renewed interest in the prospects for living organisms residing in the skies of Earth's nearest planetary neighbor. As a disequlibrium species, PH_3 is readily photolyzed and chemically reacts with H, OH and H_2O. In addition, PH_3 interacting with the ubiquitous H_2SO_4 cloud particles readily converts into phosphorous and phosphoric acids (H_3PO_3 and H_3PO_4, respectively). Together, these limit the mean lifetime of PH_3 molecules in the Venusian clouds to 50^o. Onboard instrumentation would sample the environment over all times of day including the composition of the air and aerosols, including (1) phosphorous compounds potentially linked to life processes, (2) UV-absorbing materials which possibly are also linked to astrobiology, (3) the reactive sulfur-cycle gases that create the dominant H_2SO_4 aerosols, and (4) the noble gases, their isotopes and the isotopes of light gases \textemdash key to understanding the formation and evolution of the planet and its atmosphere. A digital holographic microscope would image particles in three dimensions at 0.7 micron-scale spatial resolution, searching for cellular morphologies. The balloon mission also directly and continuously measures the pressure/temperature structure, and, supported by balloon- tracking orbiter, winds in all three dimensions. The aerobot, capable of multiple 10-km-altitude traverses centered near 55-km (\raisebox-0.5ex~0.5 bar, 25C), would enable 3-dimensional maps of these environmental characteristics as well as the dynamically/chemically influenced size distribution of aerosol particles via a nephelometer/particle-counter(Renard et al., 2020) testing, for example, the life cycle hypothesis of Seager et al (2020). These traverses also reveal the vertically- varying characteristics of atmospheric stability, gravity and planetary waves and Hadley cells, important for understanding the mechanisms that power and sustain the planet's strong super- rotation. Such altitude excursions also enable measurements of radiative balance and solar energy deposition via a Net Flux Radiometer (Aslam et al., 2015), another key to understanding super-rotation. \\\\References: Aslam, S., et al. (2015) EPSC Abstracts, Vol 10. EPSC2015-388. Baines, K. H. et al. (2020). New-Frontiers Class In-Situ Exploration of Venus: The Venus Climate and Geophysics Mission Concept. White paper submitted to Planetary Science Decadal Survey 2023-2032. Gilmore, M.S., Beauchamp. P. M., Lynch, R., Amato, M. J., et al. (2020). Venus Flagship Mission Decadal Study Final Report. https://www.lpi.usra.edu/vexag/reports/Venus-Flagship- Mission_FINAL.pdf Greaves JS., Richards MS., Bains W. et al. (2020) Phosphine in the cloud decks of Venus. Nature Astronomy doi.org/10.1038/s41550-020-1174-4. Renard, J.-B., Mousis, O., Rannou, P., Levasseur-Regourd, A. C., Berthet, G., Geffrin, J.-M., Hadamcik, E., Verdier, N., Millet, A.-L., and Daugeron, D. (2020) Counting and phase function measurements with the LONSCAPE instrument to determine physical properties of aerosols in ice giant planet atmospheres, Space Science Reviews, 206, 28. Seager S, Petkowski JJ, Gao P, et al. (2020) A proposed life cycle for persistence of the Venusian aerial biosphere. Astrobiology 2021, 21:2. DOI: 10.1089/ast.2020.224