Two-Electrons One-Photon K X-Ray Decay Rate For Ni

1981 ◽  
pp. 281-284
Author(s):  
G. Jalbert ◽  
G. B. Baptista ◽  
E. C. Montenegro
Keyword(s):  
Decay Rate ◽  
X Ray

scholarly journals The dark matter interpretation of the 3.5-keV line is inconsistent with blank-sky observations

Science ◽  
2020 ◽  
Vol 367 (6485) ◽  
pp. 1465-1467 ◽  
Author(s):  
Christopher Dessert ◽  
Nicholas L. Rodd ◽  
Benjamin R. Safdi
Keyword(s):  
Dark Matter ◽  
Emission Line ◽  
Decay Rate ◽  
Milky Way ◽  
Line Emission ◽  
Mass Range ◽  
Sterile Neutrinos ◽  
X Ray ◽  
Upper Limit ◽  
Nearby Galaxies

Observations of nearby galaxies and galaxy clusters have reported an unexpected x-ray emission line around 3.5 kilo–electron volts (keV). Proposals to explain this line include decaying dark matter—in particular, that the decay of sterile neutrinos with a mass around 7 keV could match the available data. If this interpretation is correct, the 3.5-keV line should also be emitted by dark matter in the halo of the Milky Way. We used more than 30 megaseconds of XMM-Newton (X-ray Multi-Mirror Mission) blank-sky observations to test this hypothesis, finding no evidence of the 3.5-keV line emission from the Milky Way halo. We set an upper limit on the decay rate of dark matter in this mass range, which is inconsistent with the possibility that the 3.5-keV line originates from dark matter decay.

Lifetime and Stability of Carbon Cold Cathodes

1999 ◽  
Vol 558 ◽  
Author(s):  
R. L. Fink ◽  
L. H. Thuesen ◽  
Z. Li Tolt ◽  
Zvi Yaniv ◽  
Colleen M. Marrese
Keyword(s):  
Partial Pressure ◽  
Decay Rate ◽  
Hydrogen Gas ◽  
Operating Conditions ◽  
X Ray ◽  
Display Devices ◽  
Electron Sources ◽  
Vacuum Chambers ◽  
Cold Cathodes ◽  
Initial Results

ABSTRACTWe present the results of tests measuring the life of carbon cold cathodes and determining what conditions limit the life of the cathode. Cathode life and stability are important for a broad range of applications, including displays, electron sources for satellite thrusters, x-ray tubes and microwave devices. Cathodes were tested in vacuum chambers using different gas environments as well as in sealed and gettered glass envelopes. We measured emission current half-lives of 10,000 - 20,000 hours or more in sealed display devices, depending on operating conditions. The presence of a significant oxygen or water partial pressure degrades the life of the cathode. After removing the gases the decay rate was restored to near the original value. A similar partial pressure of hydrogen gas has little or no effect on the life of the cathode. Initial results of operation in a xenon environment indicate carbon cold cathodes are much more robust compared to microtip cathodes. These results will be discussed with respect to the various applications considered for carbon cold cathodes.

scholarly journals A CORRELATION BETWEEN THE INTRINSIC BRIGHTNESS AND AVERAGE DECAY RATE OF GAMMA-RAY BURST X-RAY AFTERGLOW LIGHT CURVES

2016 ◽  
Vol 826 (1) ◽  
pp. 45 ◽  
Author(s):  
J. L. Racusin ◽  
S. R. Oates ◽  
M. de Pasquale ◽  
D. Kocevski
Keyword(s):  
Decay Rate ◽  
Gamma Ray ◽  
Light Curves ◽  
Gamma Ray Burst ◽  
X Ray

Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

1994 ◽  
Vol 144 ◽  
pp. 275-277
Author(s):  
M. Karlický ◽  
J. C. Hénoux
Keyword(s):  
Time Distribution ◽  
Electron Bombardment ◽  
Spatial Evolution ◽  
Superthermal Electrons ◽  
Flare Loop ◽  
X Ray ◽  
Superthermal Electron ◽  
Flare Loops ◽  
Chromospheric Evaporation ◽  
Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

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