Optical Bleaching of F Centers and M Centers in KCI under High Pressures

1980 ◽  
Vol 102 (1) ◽  
pp. K45-K49
Author(s):  
T. Toyama ◽  
M. Ishiguro
Keyword(s):  
High Pressures ◽  
Optical Bleaching ◽  
F Centers

The Effect of Hydrogen on the Charge States of Oxygen Vacancies in Thermochemically Reduced Alkaline-Earth Oxides

1989 ◽  
Vol 152 ◽  
Author(s):  
Y. Chen ◽  
V. M. Orera ◽  
R. Gonzalezv ◽  
R. T. Williams ◽  
G. P. Williams ◽  
...  
Keyword(s):  
Hydrogen Concentration ◽  
Alkaline Earth ◽  
Oxygen Vacancies ◽  
High Pressures ◽  
Metallic Cation ◽  
Thermochemical Reduction ◽  
The One ◽  
Oxide Crystals ◽  
Positively Charged ◽  
F Centers

To a greater or lesser extent, all alkaline-earth oxide crystals contain hydrogen. Thermochemical reduction (TCR) of MgO and CaO crystals at high temperatures (˜2000K) and high pressures (4 to 7 atmospheres) of the metallic cation vapor (Mg and Ca respectively) results in a stoichiometric deficiency of oxygen ions, creating F centers (oxygen vacancies each with two electrons) and H− ions (protons in the anion sublattice, each occupied by two electrons). The positively-charged H− ions serve as traps for electrons excited from the F centers. Steady-state photo-excitation of the F absorption band results in F luminescence which typically extends to several minutes. This photoluminescence is detrimental for certain applications, such as tunable lasers. We have been able to reduce the hydrogen concentration prior to TCR of MgO and during TCR of CaO. The result is that the oxygen vacancies are predominantly in the one-electron F+ charge state. In contrast to the F luminescence, the decay of the F+ luminescence does not exhibit long phosphorescence. The prevalence of the F+ over the F state is found to be a function not only of the hydrogen concentration but also the severity of the thermochemical reduction.

Der Einfluß der Elektronenaffinität auf die optisch stimulierte Exoelektronenemission von KCl / Influence of the Electron Affinity on the Optically Stimulated Exoelectron Emission (OSEE) of KCl

1974 ◽  
Vol 29 (12) ◽  
pp. 1922-1924
Author(s):  
W. Kriegseis ◽  
A. Scharmann ◽  
J. Seibert
Keyword(s):  
Single Crystals ◽  
Electron Affinity ◽  
Strong Dependence ◽  
Electron Bombardment ◽  
Gas Pressure ◽  
Exoelectron Emission ◽  
Residual Gas ◽  
Optical Bleaching ◽  
F Centers

The OSEE of KCl single crystals due to optical bleaching of F-centers created by electron bombardment has been investigated under various vacuum conditions. Its decay and intensity revealed a strong dependence on the residual gas pressure which can be explained by alterations of the electron affinity.

Optical Bleaching of F-Centers in BaFCl Crystals after X-Irradiation at Room Temperature

1988 ◽  
Vol 149 (2) ◽  
pp. K101-K104 ◽  
Author(s):  
K. Inabe ◽  
S. Nakamura ◽  
N. Takeuchi
Keyword(s):  
Room Temperature ◽  
X Irradiation ◽  
Optical Bleaching ◽  
F Centers

A first-principles Hartree-Fock description of MnO at high pressures

1998 ◽  
Vol 77 (4) ◽  
pp. 1063-1075
Author(s):  
W. C. Mackrodt, E.-A. Williamson, D. W
Keyword(s):  
First Principles ◽  
High Pressures ◽  
Hartree Fock

Stability of diamond at high pressures

1987 ◽  
Vol 152 (6) ◽  
pp. 317 ◽  
Author(s):  
A.F. Goncharov
Keyword(s):  
High Pressures
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