Metastable Percolation Phase Formation in Lif Implanted with Alkali Ions

1981 ◽  
Vol 7 ◽  
Author(s):  
J. Davenas ◽  
P. Thevenard ◽  
C. Dupuy
Keyword(s):  
Low Temperature ◽  
Optical Absorption ◽  
Phase Formation ◽  
Room Temperature ◽  
Critical Concentration ◽  
External Perturbation ◽  
Metallic Layer ◽  
Alkali Ions ◽  
Conducting State ◽  
Equilibrium Situation

ABSTRACTThe formation of a continuous metallic layer in the doped region of LiF crystals implanted at low temperature, has been explained by the formation of bridges between next neighbouring alkali ions of the lattice around-each implanted ion. For a critical concentration of implanted ions it is possible to show using statistical arguments that conducting chains are formed by the union of these links, according to a percolation mechanism. We show that the assumption of a distribution of isolated implanted ions at low temperature is justified by the observation of their precipitation when the crystal is warmed up to room temperature. The transformation of the metallic optical absorption into the colloidal band associated with precipitates of implanted ions is correlated with the transition from a conducting state to an insulating state of the implanted layer. We show that this evolution towards an equilibrium situation may be reversed by a reirradiation, which is used as an external perturbation and that the conducting state associated with dispersed implanted ions is then once again obtained.

Radiation Damage Mechanisms In Scintillator Materials: Applications to BaF2 and CeF3

1994 ◽  
Vol 348 ◽  
Author(s):  
L. E. Halliburton ◽  
G. J. Edwards
Keyword(s):  
Low Temperature ◽  
Optical Absorption ◽  
Radiation Damage ◽  
Room Temperature ◽  
Epr Spectrum ◽  
Absorption Bands ◽  
Paramagnetic Resonance ◽  
Damage Mechanisms ◽  
Temperature Damage ◽  
F Centers

ABSTRACTResults from recent radiation damage studies in high quality BaF2 and CeF3 crystals are presented. Optical absorption and electron paramagnetic resonance (EPR) techniques are used to identify specific radiation damage mechanisms. Specific attention is given to the role of oxygen and hydrogen in the room temperature damage of BaF2. Also, Mn2+ ions are shown to change valence state in BaF2during room temperature irradiation. Numerous optical absorption bands are created in CeF3 during irradiations at low temperature. These bands are associated with electron traps (either F centers or Ce2+ ions) and they thermal anneal below room temperature. An EPR spectrum, assigned to F centers, is observed in low-temperature irradiated CeF3.

scholarly journals Low-Temperature Luminescent Studies of Emissive Guanine Substitute for the Detection of Biopolymers

2020 ◽  
Vol 65 (4) ◽  
pp. 317
Author(s):  
V. Yu. Kudrya ◽  
V. M. Yashchuk ◽  
A. P. Naumenko ◽  
Y. Mely ◽  
Ya. O. Gumenyuk
Keyword(s):  
Energy Transfer ◽  
Low Temperature ◽  
Optical Absorption ◽  
Fluorescence Spectra ◽  
Room Temperature ◽  
Band Maximum ◽  
Frozen Solution ◽  
Buffer Solutions ◽  
Long Wave ◽  
Fluorescence And Phosphorescence

The optical absorption at 300 K and the fluorescence and phosphorescence at 78 K of the emissive guanine substitute, deoxythienoguanosine, (dthG) were investigated in aqueous and TRIS-HCl-buffer solutions. Two optical absorption and fluorescence centers at room temperature were attributed to two keto-enol tautomers of dthG, which confirms previously obtained results. In contrast to room temperature, only one emission band was observed at 78 K in fluorescence spectra that was close to the long-wave fluorescence band at room temperature and could be associated with the tautomer with long-wave absorption. This phenomenon can be explained by the energy transfer by excitations in a frozen solution between two types of the optical centers mentioned above. The similar conclusion is drawn for the phosphorescence: only one tautomer phosphorescence band is observed. The spectral positions of this band maximum are essentially different for aqueous and buffer solutions (∼50 nm).

Survival of mouse blastocysts after low-temperature preservation under high pressure

2004 ◽  
Vol 52 (4) ◽  
pp. 479-487 ◽  
Author(s):  
Cs. Pribenszky ◽  
M. Molnár ◽  
S. Cseh ◽  
L. Solti
Keyword(s):  
Phase Transition ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
High Hydrostatic Pressure ◽  
Room Temperature ◽  
Freezing Point ◽  
Significant Loss ◽  
Embryo Cryopreservation ◽  
Subzero Temperatures ◽  
Survival Capacity

Cryoinjuries are almost inevitable during the freezing of embryos. The present study examines the possibility of using high hydrostatic pressure to reduce substantially the freezing point of the embryo-holding solution, in order to preserve embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The pressure of 210 MPa lowers the phase transition temperature of water to -21°C. According to the results of this study, embryos can survive in high hydrostatic pressure environment at room temperature; the time embryos spend under pressure without significant loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C significantly reduced the survival capacity of the embryos; gradual decompression had no beneficial effect on survival at that stage. Based on the findings, the use of the phenomena is not applicable in this form, since pressure and low temperature together proved to be lethal to the embryos in these experiments. The application of hydrostatic pressure in embryo cryopreservation requires more detailed research, although the experience gained in this study can be applied usefully in different circumstances.

Low‐temperature phase formation in the SrF 2 ‐ LaF 3 system

2020 ◽  
Author(s):  
Pavel P. Fedorov ◽  
Alexander A. Alexandrov ◽  
Valery V. Voronov ◽  
Maria N. Mayakova ◽  
Alexander E. Baranchikov ◽  
...  
Keyword(s):  
Low Temperature ◽  
Phase Formation ◽  
Temperature Phase ◽  
Low Temperature Phase

Photophysical properties of N719 and Z907 dyes, benchmark sensitizers for dye-sensitized solar cells, at room and low temperature

2021 ◽  
Vol 23 (10) ◽  
pp. 6182-6189
Author(s):  
Dariusz M. Niedzwiedzki
Keyword(s):  
Solar Cells ◽  
Low Temperature ◽  
Optical Spectroscopy ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Dye Sensitized Solar Cells ◽  
Time Resolved ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Photophysical properties of N719 and Z907, benchmark Ru-dyes used as sensitizers in dye-sensitized solar cells, were studied by static and time-resolved optical spectroscopy at room temperature and 160 K.

Transition Insulator-Metal and Antiferromagnetic-Paramagnetic Cu Doped in La0.47Ca0.53MnO3

2015 ◽  
Vol 1123 ◽  
pp. 73-77 ◽  
Author(s):  
Yohanes Edi Gunanto ◽  
K. Sinaga ◽  
B. Kurniawan ◽  
S. Poertadji ◽  
H. Tanaka ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Magnetic Structure ◽  
Room Temperature ◽  
Paramagnetic Phase ◽  
Perovskite Manganites ◽  
Antiferromagnetic Phase ◽  
Temperature Transition ◽  
Cu Doping ◽  
Metal State

The study of the perovskite manganites La0.47Ca0.53Mn1-xCuxO3 with x = 0, 0.06, 0.09, and 0.13 has been done. The magnetic structure was determined using high-resolution neutron scattering at room temperature and low temperature. All samples were paramagnetic at room temperature and antiferromagnetic at low temperature. Using the SQUID Quantum Design, the samples showed that the doping of the insulating antiferromagnetic phase La0.47Ca0.53MnO3 with Cu doping resulted in the temperature transition from an insulator to metal state, and an antiferromagnetic to paramagnetic phase. The temperature transition from an insulator to metal state ranged from 23 to 100 K and from 200 to 230 K for the transition from an antiferromagnetic to paramagnetic phase.

Critical concentration of Mg addition for plastic instabilities in Al–Mg alloys

2000 ◽  
Vol 15 (5) ◽  
pp. 1037-1040 ◽  
Author(s):  
N. Q. Chinh ◽  
F. Csikor ◽  
Zs. Kovács ◽  
J. Lendvai
Keyword(s):  
Room Temperature ◽  
Loading Rate ◽  
Critical Concentration ◽  
Solute Concentration ◽  
Mg Alloys ◽  
Depth Sensing ◽  
Solute Content ◽  
Mg Addition ◽  
Constant Loading Rate ◽  
Al Mg Alloys

Plastic instabilities were investigated by the depth-sensing microhardness test in binary high-purity Al–Mg alloys with different Mg contents. During the tests the applied load was increased from 0 to 2000 mN at constant loading rate. The instabilities appeared as characteristic steps in the load–depth curves during indentation. It was shown that the occurrence and development of the plastic instabilities depend strongly on the solute content. Furthermore, the plastic instabilities occurred only when the solute concentration was larger than a critical value, C0. From room-temperature tests on Al–Mg alloys, C0 was found to be 0.86 wt% Mg. The critical concentration, which is necessary to get plastic instabilities, was also interpreted theoretically.

Molecule-Based Magnets—An Overview

MRS Bulletin ◽  
2000 ◽  
Vol 25 (11) ◽  
pp. 21-30 ◽  
Author(s):  
Joel S. Miller ◽  
Arthur J. Epstein
Keyword(s):  
Low Temperature ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Low Density ◽  
Materials Properties ◽  
The Common ◽  
New Processing ◽  
Very High

Molecule-based magnets are a broad, emerging class of magnetic materials that expand the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal and rare-earth-based magnets can be found in molecule-based magnets. Although discovered less than two decades ago, magnets with ordering temperatures exceeding room temperature, very high (∼27.0 kOe or 2.16 MA/m) and very low (several Oe or less) coercivities, and substantial remanent and saturation magnetizations have been achieved. In addition, exotic phenomena including photoresponsiveness have been reported. The advent of molecule-based magnets offers new processing opportunities. For example, thin-film magnets can be prepared by means of low-temperature chemical vapor deposition and electrodeposition methods.

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