scholarly journals Observations of a mix of cold and warm electrons by RPC-MIP at 67P/Churyumov-Gerasimenko

2020 ◽  
Vol 640 ◽  
pp. A110
Author(s):  
N. Gilet ◽  
P. Henri ◽  
G. Wattieaux ◽  
N. Traoré ◽  
A. I. Eriksson ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Ratio ◽  
Special Focus ◽  
Temperature Plasma ◽  
Total Electron Density ◽  
Total Electron ◽  
Mutual Impedance ◽  
Impedance Probe ◽  
Resonance Principle ◽  
Cold Electrons

Context. The Mutual Impedance Probe (MIP) of the Rosetta Plasma Consortium (RPC) onboard the Rosetta orbiter which was in operation for more than two years, between August 2014 and September 2016 to monitor the electron density in the cometary ionosphere of 67P/Churyumov-Gerasimenko. Based on the resonance principle of the plasma eigenmodes, recent models of the mutual impedance experiment have shown that in a two-electron temperature plasma, such an instrument is able to separate the two isotropic electron populations and retrieve their properties. Aims. The goal of this paper is to identify and characterize regions of the cometary ionized environment filled with a mix of cold and warm electron populations, which was observed by Rosetta during the cometary operation phase. Methods. To reach this goal, this study identifies and investigates the in situ mutual impedance spectra dataset of the RPC-MIP instrument that contains the characteristics of a mix of cold and warm electrons, with a special focus on instrumental signatures typical of large cold-to-total electron density ratio (from 60 to 90%), that is, regions strongly dominated by the cold electron component. Results. We show from the observational signatures that the mix of cold and warm cometary electrons strongly depends on the cometary latitude. Indeed, in the southern hemisphere of 67P, where the neutral outgassing activity was higher than in northern hemisphere during post-perihelion, the cold electrons were more abundant, confirming the role of electron-neutral collisions in the cooling of cometary electrons. We also show that the cold electrons are mainly observed outside the nominal electron-neutral collision-dominated region (exobase), where electrons are expected to have cooled down. This which indicates that the cold electrons have been transported outward. Finally, RPC-MIP detected cold electrons far from the perihelion, where the neutral outgassing activity is lower, in regions where no electron exobase was expected to have formed. This suggests that the cometary neutrals provide a more frequent or efficient cooling of the electrons than expected for a radially expanding ionosphere.

Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K

2017 ◽  
Vol 73 (4) ◽  
pp. 654-659 ◽  
Author(s):  
Zhijie Chua ◽  
Bartosz Zarychta ◽  
Christopher G. Gianopoulos ◽  
Vladimir V. Zhurov ◽  
A. Alan Pinkerton
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Topological Analysis ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Total Electron Density ◽  
Total Electron ◽  
Structure Factors ◽  
Density Analysis ◽  
Experimental Charge Density

A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The similarity of the properties of the total electron density in all cases demonstrates the robustness of the Hansen–Coppens formalism. All intra- and intermolecular interactions have been characterized.

Electron densities and the VSEPR model of molecular geometry

1992 ◽  
Vol 70 (3) ◽  
pp. 742-750 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Electron Density ◽  
Present Status ◽  
Electron Pair ◽  
Molecular Geometry ◽  
Physical Basis ◽  
Valence Shell ◽  
Electron Densities ◽  
Total Electron Density ◽  
Total Electron

This paper reviews the present status of the VSEPR model of molecular geometry in relation to electron densities. The discussion is based on the electron pair domain version of this model. The fundamental postulates of the model are summarized and illustrated by a discussion of the structures of some molecules with five and seven electron pair domains in the valence shell, including the recently discovered ions XeF5− and XeOF6−. The total electron density does not provide any obvious support for the model and although electron density deformation maps do provide some support they are not always reliable. The Laplacian of the electron density, however, shows the presence of valence shell charge concentrations that correspond closely in number and properties to the electron pair domains of the VSEPR model. This correspondence between electron pair domains and valence shell charge concentrations provides a physical basis for a better understanding of the VSEPR model. Keywords: VSEPR model, electron densities, molecular geometry, Laplacian of the electron density, electron pair domain.

Total electron density from thes-electron density

1998 ◽  
Vol 57 (5) ◽  
pp. 3458-3461 ◽  
Author(s):  
Á. Nagy ◽  
E. Bene
Keyword(s):  
Electron Density ◽  
Total Electron Density ◽  
Total Electron

scholarly journals Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument

2020 ◽  
Vol 638 ◽  
pp. A124
Author(s):  
Gaëtan Wattieaux ◽  
Pierre Henri ◽  
Nicolas Gilet ◽  
Xavier Vallières ◽  
Jan Deca
Keyword(s):  
Temperature Ratio ◽  
Electron Densities ◽  
Plasma Parameters ◽  
Mutual Impedance ◽  
Rosetta Mission ◽  
Fluctuation Range ◽  
Impedance Probe ◽  
Cold Electrons ◽  
Two Populations ◽  
Comet 67P

The plasma of comet 67P/Churyumov-Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were fit on experimental responses acquired from January to September 2016 to extract the electron densities and temperatures. A time-tracking of the plasma parameters was performed, leading to the identification of a cold and a warm population of electrons during the period of interest. The respective densities and temperatures lie in the ranges [100; 1000] cm−3 and [0.05; 0.3] eV for the cold electrons and in the ranges [50; 500] cm−3 and [2; 10] eV for the warm electrons. Warm electrons most of the time made up between 10 and 30% of the whole population, while the temperature ratio between warm and cold electrons lay mostly between 30 and 70 during the period we studied. The fluctuation range of the plasma parameters, that is, the electron densities and temperatures, appears to have remained rather constant during the last nine months of the mission. We take the limitations of the instrument that are due to the experimental noise into account in our discussion of the results.

scholarly journals Early results from the Whisper instrument on Cluster: an overview

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1241-1258 ◽  
Author(s):  
P. M. E. Décréau ◽  
P. Fergeau ◽  
V. Krasnoselskikh ◽  
E. Le Guirriec ◽  
M. Lévêque ◽  
...  
Keyword(s):  
Electron Density ◽  
Small Scale ◽  
Data Sets ◽  
Total Density ◽  
Total Electron Density ◽  
Data Set ◽  
Total Electron ◽  
Density Data ◽  
Early Results ◽  
Natural Emissions

Abstract. The Whisper instrument yields two data sets: (i) the electron density determined via the relaxation sounder, and (ii) the spectrum of natural plasma emissions in the frequency band 2–80 kHz. Both data sets allow for the three-dimensional exploration of the magnetosphere by the Cluster mission. The total electron density can be derived unambiguously by the sounder in most magnetospheric regions, provided it is in the range of 0.25 to 80 cm-3 . The natural emissions already observed by earlier spacecraft are fairly well measured by the Whisper instrument, thanks to the digital technology which largely overcomes the limited telemetry allocation. The natural emissions are usually related to the plasma frequency, as identified by the sounder, and the combination of an active sounding operation and a passive survey operation provides a time resolution for the total density determination of 2.2 s in normal telemetry mode and 0.3 s in burst mode telemetry, respectively. Recorded on board the four spacecraft, the Whisper density data set forms a reference for other techniques measuring the electron population. We give examples of Whisper density data used to derive the vector gradient, and estimate the drift velocity of density structures. Wave observations are also of crucial interest for studying small-scale structures, as demonstrated in an example in the fore-shock region. Early results from the Whisper instrument are very encouraging, and demonstrate that the four-point Cluster measurements indeed bring a unique and completely novel view of the regions explored.Key words. Space plasma physics (instruments and techniques; discontinuities, general or miscellaneous)

Acrylonitrile (AN)–Cu9(100) interfaces: Electron distribution and nature of bonded interactions

2003 ◽  
Vol 81 (6) ◽  
pp. 542-554 ◽  
Author(s):  
Petar M Mitrasinovic
Keyword(s):  
Electron Density ◽  
Molecular Orbital ◽  
Density Functional ◽  
Electron Distribution ◽  
Atomic Orbital ◽  
Interfacial Interactions ◽  
Total Electron Density ◽  
Total Electron ◽  
Topological Features ◽  
The One

There is a fundamental interest in the investigation of the interfacial interactions and charge migration processes between organic molecules and metallic surfaces from a theoretical standpoint. Quantum mechanical (QM) concepts of bonding are contrasted, and the vital importance of using combined QM methods to explore the nature of the interfacial interactions is established. At the one-electron level, the charge distribution and nature of bonded interactions at the AN–Cu9(100) (neutral and charged (–1)) interfaces are investigated by both the Becke (B) – Vosko (V) – Wilk (W) – Nusair (N)/DZVP density functional theory (DFT) method and the MP2/6–31+G* strategy within the conceptual framework provided by natural bond orbital (NBO) – natural atomic orbital (NAO) population analysis and Atoms-In-Molecules (AIM) theory. By this approach, the interfacial interactions are given physical definitions free of any assumptions and are visualized by using the topological features of the total electron density. A natural link between the electron density on the one side and the shapes (not energies) of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) on the other side is clarified. The question of whether the spatial extents of the HOMO and LUMO resemble the corresponding spatial maps of the negative (charge locally concentrated) and positive (charge locally depleted) Laplacian of the total electron density in [AN–Cu9(100)]–1 is addressed.Key words: AN–Cu9(100) interfaces, NBO–NAO population, electron distribution, AIM, bonded interactions.

First Principles Investigations on the Supramolecular Structure of 1,5-Diaminotetrazole

2012 ◽  
Vol 554-556 ◽  
pp. 65-69
Author(s):  
He Lin ◽  
Shun Guan Zhu ◽  
Lin Zhang ◽  
Xin Hua Peng ◽  
Hong Zhen Li
Keyword(s):  
Hydrogen Bonds ◽  
Electron Density ◽  
First Principles ◽  
Supramolecular Structure ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Intermolecular Hydrogen Bonds ◽  
Total Electron Density ◽  
Population Total ◽  
Total Electron

The supramolecular structure of 1,5-diaminotetrazole was investigated by first principles calculations, based on the plane-wave psedopotential method. The exchange-correlations potential was performed with the Perdew-Burke-Ernzerhof (PBE) functional of generalized gradient approximation (GGA). The Muliken population, total electron density and electron density difference were calculated. As a result, there are strong intramolecular and intermolecular hydrogen bonds among 1,5-diaminotetrazole molecules. The mainly reason for the formation of supramolecular structure of 1,5-diaminotetrazole is that the intermolecular hydrogen bonds of N(5)－H(5B)…N(4) and N(6)－H(6)…N(2).Moreover, chemical bond analysis showed that there are strong non-bond actions and the N(1)－N(5) bond seriously distorted was observed. The performance of 1,5-diaminotetrazole is quite related with the supramolecular structure.

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