Anthracene fluorescence at low temperatures. I. Purified single crystals

1972 ◽  
Vol 25 (7) ◽  
pp. 1411 ◽  
Author(s):  
LE Lyons ◽  
LJ Warren
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Fluorescence Spectrum ◽  
Low Temperatures ◽  
Free Exciton ◽  
Deformation Bands ◽  
Exciton Emission ◽  
Polarized Emission ◽  
Impurity Bands ◽  
Phonon Structure

The low-temperature fluorescence spectrum of purified vapour-grown anthracene single crystals is presented and the free-exciton emission distinguished from a number of defect or impurity bands present even in the purest crystals. In assigning the observed bands the symmetry of the active vibrations and the origin of background fluorescence and deformation bands are discussed. The phonon structure in the region of the fluorescence origin was found to be almost completely b-polarized. Emission of electronic origin (25103 cm-1) was too weak to be observed. Polarization ratios of the principal vibronio bands at 5.6 K are given.

Anthracene fluorescence at low temperatures. II. Doped single crystals

1972 ◽  
Vol 25 (7) ◽  
pp. 1427 ◽  
Author(s):  
LE Lyons ◽  
LJ Warren
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Low Temperatures ◽  
Exciton Emission ◽  
Host Molecules ◽  
Impurity Bands

By the addition of dopants to single crystal anthraoene it is shown that many of the fluorescence bands additional to exciton emission are due to traces of 2-methylanthracene. Other impurity bands, apparently arising from locally disorientated host molecules, appear on doping with most of the following, the effects increasing in the order given: carbazole, biphenyl, p-terphenyl, anthraquinone, naphthalene, naphthacene, phenanthrene, pyrene, chrysene. The host vibronic bands were virtually unaffected by dopants, except for small line shifts in the presence of 2-methylanthracene.

scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

The Design and Use of Special-Purpose Attachments for the Horizontal Diffractometer

1963 ◽  
Vol 7 ◽  
pp. 302-313
Author(s):  
William L. Baun ◽  
John J. Renton
Keyword(s):  
Thermal Expansion ◽  
Low Temperature ◽  
Single Crystals ◽  
Low Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Semicrystalline Polymers ◽  
Organic Liquids ◽  
Crystalline Materials ◽  
Full Circle ◽  
Beryllium Window

AbstractSeveral special-purpose attachments have been designed and built for the Siemens horizontal diffractometer. Design details and experimental results are shown for the following equipment: (1) Low-temperature mount for poly crystalline materials—examples are shown illustrating identification of organic liquids crystallized at low temperatures, and results are presented on coefficient of thermal expansion of alloys in the binary system copper—platinum from −185 to 25°C. (2) Low-temperature mount for single-crystal studies—this design allows recording of higher-level layer lines by use of a domed beryllium window. Illustrations are shown for organic single crystals and for organic liquids crystallized in the lowtemperature mount. (3) Focusing attachment—this attachment uses a curved specimen mounted on the focusing circle (Seeman-Bohlin mounting). Comparisons of dispersion are made and examples such as the (400) reflection from molybdenum are shown using both curved and flat specimens. (4) Full-circle goniometer—this device has been used primarily for determining distribution of intensity in amorphous and semicrystalline polymers, but is applicable to study of single crystals. Examples of both of these applications are discussed.

The ferromagnetic domain structure of haematite

1968 ◽  
Vol 303 (1475) ◽  
pp. 525-529 ◽  
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Domain Structure ◽  
Low Temperatures ◽  
Remanent Magnetization ◽  
Temperature Transition ◽  
Small Temperature ◽  
Temperature Range ◽  
Ferromagnetic Domain ◽  
Synthetic Crystals

Observations are reported of the ferromagnetic domain structure of natural and synthetic single crystals, made at temperatures close to the low temperature transition with the aid of an acetone based magnetic colloid. The domain structure of the synthetic crystals was found to change radically over a small temperature range centred around –12 °C. These changes are correlated with the measured remanent magnetization. Fairly extensive colloid patterns were found on the natural crystals at low temperatures but when the natural crystals were annealed at 1200 °C this low temperature colloid structure was no longer found.

Low temperature amorphization and superconductivity in FeSe single crystals at high pressures

2010 ◽  
Vol 25 (2) ◽  
pp. 396-400 ◽  
Author(s):  
Andrew K. Stemshorn ◽  
Georgiy Tsoi ◽  
Yogesh K. Vohra ◽  
Stanislav Sinogeiken ◽  
Phillip M. Wu ◽  
...  
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Single Crystals ◽  
Amorphous Phase ◽  
Tetragonal Phase ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
High Pressures ◽  
X Ray Diffraction ◽  
X Ray

In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 ± 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

LOW-TEMPERATURE TRANSITION METAL-SEMICONDUCTOR IN CdCr2Se4 SINGLE CRYSTALS DOPED WITH INDIUM AND GALLIUM

1980 ◽  
Vol 41 (C5) ◽  
pp. C5-155-C5-156 ◽  
Author(s):  
T. G. Aminov ◽  
K. P. Below ◽  
V. T. Kalinnikov ◽  
L. I. Koroleva ◽  
L. N. Tovmasjan
Keyword(s):  
Low Temperature ◽  
Transition Metal ◽  
Single Crystals ◽  
Temperature Transition
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