Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

The noble gases are elements of broad importance across science and technology and are primary constituents of planetary and stellar atmospheres, where they segregate into droplets or layers that affect the thermal, chemical, and structural evolution of their host body. We have measured the optical properties of noble gases at relevant high pressures and temperatures in the laser-heated diamond anvil cell, observing insulator-to-conductor transformations in dense helium, neon, argon, and xenon at 4,000–15,000 K and pressures of 15–52 GPa. The thermal activation and frequency dependence of conduction reveal an optical character dominated by electrons of low mobility, as in an amorphous semiconductor or poor metal, rather than free electrons as is often assumed for such wide band gap insulators at high temperatures. White dwarf stars having helium outer atmospheres cool slower and may have different color than if atmospheric opacity were controlled by free electrons. Helium rain in Jupiter and Saturn becomes conducting at conditions well correlated with its increased solubility in metallic hydrogen, whereas a deep layer of insulating neon may inhibit core erosion in Saturn.

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Binary mixtures of water + five noble gases: comparison of binodal and critical curves at high pressures

Fluid Phase Equilibria ◽

10.1016/s0378-3812(96)90003-5 ◽

1996 ◽

Vol 123 (1-2) ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Ya Song Wei ◽

Richard J. Sadus ◽

E. Ulrich Franck

Keyword(s):

Binary Mixtures ◽

High Pressures ◽

Noble Gases ◽

Critical Curves

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How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

Molecules ◽

10.3390/molecules24162933 ◽

2019 ◽

Vol 24 (16) ◽

pp. 2933 ◽

Cited By ~ 12

Author(s):

Ranajit Saha ◽

Gourhari Jana ◽

Sudip Pan ◽

Gabriel Merino ◽

Pratim Kumar Chattaraj

Keyword(s):

Electron Density ◽

High Pressures ◽

Noble Gases ◽

Activation Barrier ◽

Covalent Bond ◽

The Other ◽

Personal Account ◽

Covalent Bonds ◽

Other Hand ◽

Different Types

Noble gases (Ngs) are the least reactive elements in the periodic table towards chemical bond formation when compared with other elements because of their completely filled valence electronic configuration. Very often, extreme conditions like low temperatures, high pressures and very reactive reagents are required for them to form meaningful chemical bonds with other elements. In this personal account, we summarize our works to date on Ng complexes where we attempted to theoretically predict viable Ng complexes having strong bonding to synthesize them under close to ambient conditions. Our works cover three different types of Ng complexes, viz., non-insertion of NgXY type, insertion of XNgY type and Ng encapsulated cage complexes where X and Y can represent any atom or group of atoms. While the first category of Ng complexes can be thermochemically stable at a certain temperature depending on the strength of the Ng-X bond, the latter two categories are kinetically stable, and therefore, their viability and the corresponding conditions depend on the size of the activation barrier associated with the release of Ng atom(s). Our major focus was devoted to understand the bonding situation in these complexes by employing the available state-of-the-art theoretic tools like natural bond orbital, electron density, and energy decomposition analyses in combination with the natural orbital for chemical valence theory. Intriguingly, these three types of complexes represent three different types of bonding scenarios. In NgXY, the strength of the donor-acceptor Ng→XY interaction depends on the polarizing power of binding the X center to draw the rather rigid electron density of Ng towards itself, and sometimes involvement of such orbitals becomes large enough, particularly for heavier Ng elements, to consider them as covalent bonds. On the other hand, in most of the XNgY cases, Ng forms an electron-shared covalent bond with X while interacting electrostatically with Y representing itself as [XNg]+Y−. Nevertheless, in some of the rare cases like NCNgNSi, both the C-Ng and Ng-N bonds can be represented as electron-shared covalent bonds. On the other hand, a cage host is an excellent moiety to examine the limits that can be pushed to attain bonding between two Ng atoms (even for He) at high pressure. The confinement effect by a small cage-like B12N12 can even induce some covalent interaction within two He atoms in the He2@B12N12 complex.

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Empirical surface gravities

Symposium - International Astronomical Union ◽

10.1017/s0074180900116596 ◽

1997 ◽

Vol 189 ◽

pp. 119-124

Author(s):

P. F. L. Maxted

Keyword(s):

Binary Stars ◽

Short Review ◽

Limited Range ◽

Stellar Atmospheres ◽

Fundamental Parameter ◽

Dwarf Stars ◽

Eclipsing Binary ◽

White Dwarf Stars ◽

Eclipsing Binary Stars ◽

Order Of Magnitude

The surface gravity of a star (log g) is a fundamental parameter in models of stellar atmospheres. Given suitable spectra, log g can be determined from such models with an accuracy of 0.1dex, at best. Detached eclipsing binary stars can provide values of log g an order of magnitude more accurate than this, though for a more limited range of stars. Naturally, less accurate surface gravities can be obtained for a wider range of eclipsing binary stars.These facts are well known, so in this short review I will outline the types of stars to which the two methods have be usefully applied and might be applied in the near future. This naturally leads to the question of where the two ranges overlap and the comparison of results from the two methods. Techniques for allowing this comparison to made directly will be described. Surface gravities derived from winds in hot stars and (indirectly) from gravitational redshifts in white dwarf stars will also be covered briefly.

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Amorphization and structural evolution of - and its high density polymorph - at high pressures

Journal of Physics and Chemistry of Solids ◽

10.1016/j.jpcs.2007.07.130 ◽

2008 ◽

Vol 69 (1) ◽

pp. 35-40 ◽

Cited By ~ 4

Author(s):

G.D. Mukherjee ◽

A.S. Karandikar ◽

V. Vijayakumar ◽

B.K. Godwal ◽

S.N. Achary ◽

...

Keyword(s):

High Pressures ◽

Structural Evolution ◽

High Density

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Effect of HIP Parameters on the Micro-Structural Evolution of a Single Crystal Ni-Based Superalloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.278.72 ◽

2011 ◽

Vol 278 ◽

pp. 72-77 ◽

Cited By ~ 5

Author(s):

Inmaculada Lopez-Galilea ◽

Stephan Huth ◽

Marion Bartsch ◽

Werner Theisen

Keyword(s):

Single Crystal ◽

Atmospheric Pressure ◽

High Pressures ◽

Hot Isostatic Pressing ◽

Structural Evolution ◽

Local Deformation ◽

Local Distribution ◽

Slow Cooling ◽

Distribution Of Elements ◽

Hardened State

For reducing the porosity of single crystal (SX) nickel-based superalloys, Hot Isostatic Pressing (HIP) is used. High pressures of about 100-170 MPa lead to local deformation, which close the pores. However, since HIP also requires high temperatures (1000-1200°C) it has a pronounced effect on the microstructure and the local distribution of elements. This contribution analyses the effect of different HIP treatments on both the microstructure and the segregation of the SX superalloy LEK94 in the as-precipitation-hardened state. In addition, the effects of rapid or slow cooling are analyzed. To distinguish the effect of pressure from those of temperature, the HIPed samples are compared with specimens annealed at atmospheric pressure.

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Electronic stopping of protons in xenon plasmas due to free and bound electrons

Laser and Particle Beams ◽

10.1017/s0263034612000900 ◽

2013 ◽

Vol 31 (1) ◽

pp. 105-111 ◽

Cited By ~ 6

Author(s):

Manuel D. Barriga-Carrasco ◽

David Casas

Keyword(s):

Oscillator Strength ◽

Close Agreement ◽

Noble Gases ◽

Previous Literature ◽

Free Electrons ◽

Hartree Fock ◽

Plasma Target ◽

Strength Functions ◽

Bound Electrons

AbstractIn this work, proton stopping due to free and bound electrons in a plasma target is analyzed. The stopping of free electrons is calculated using the dielectric formalism, well described in previous literature. In the case of bound electrons, Hartree-Fock methods and oscillator strength functions are used. Differences between both stopping, due to free and bound electrons, are shown in noble gases. Then, enhanced plasma stopping can be easily estimated from target ionization. Finally, we compare our calculations with an experiment in xenon plasmas finding a close agreement.

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