Raman Spectra of Hexagonal Ethylsulfates of Yttrium and of some Rare Earths

1973 ◽  
Vol 51 (7) ◽  
pp. 1023-1031 ◽  
Author(s):  
G. Schaack ◽  
J. A. Koningstein
Keyword(s):  
Theoretical Calculation ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Raman Spectra ◽  
Rare Earths ◽  
Low Temperatures ◽  
Laser Excitation ◽  
Electronic Transitions ◽  
Line Widths

The phonon Raman spectra of single crystals of Y(C2H5SO4)3•9H2O, Ce(C2H5SO4)3•9H2O, Nd(C2H5SO4)3•9H2O, Sm(C2H5SO4)3•9H2O have been studied at low temperatures with laser excitation. Some information has also been obtained of the compounds of Ho3+ and Er3+. The types of symmetry of the observed modes have been determined and compared with the results of a group theoretical calculation. The internal modes of the C2H5 and SO4 groups and of the H2O molecules can be completely attributed to observed transitions. There is some evidence to attribute the librational modes of the H2O molecules to transitions which show a very pronounced temperature dependence of the line-widths. Reasons for this temperature dependence are discussed. No lines have been found that can be attributed uniquely to electronic transitions.

New Developments in Raman Spectroscopy with Lasers: Electronic Transitions

1968 ◽  
Vol 22 (5) ◽  
pp. 438-444 ◽  
Author(s):  
J. A. Koningstein
Keyword(s):  
Raman Spectroscopy ◽  
Single Crystals ◽  
Crystal Field ◽  
Raman Spectra ◽  
Raman Effect ◽  
Electronic Transitions ◽  
New Developments ◽  
Selection Rules ◽  
Phonon Spectra ◽  
Host Lattices

A discussion is given of the Raman spectra of single crystals of yttrium gallium garnet (YGaG), of ytterbrium gallium garnet (YbGaG), and of Yb:YGaG. From a comparison of the spectra it has been possible to separate the phonon spectra of the host lattices from that of an electronic Raman effect which occurs between the crystal field levels of the 2F7/2 manifold of Yb3+ in the garnet crystals. Information with respect to the selection rules governing both types of spectra is given.

Structure of tetrakis(dimethylamino)ethene (TDAE) at low temperatures

1995 ◽  
Vol 210 (7) ◽  
Author(s):  
J. Bruckmann ◽  
C. Krüger ◽  
H. Borrmann ◽  
A. Simon ◽  
H. Bock
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Low Temperatures ◽  
Structure Refinement ◽  
Static Disorder ◽  
Structural Details ◽  
Different Temperatures

AbstractThe single crystal structure of TDAE was redetermined at different temperatures. Phase transitions are observed by warming the samples from low temperatures but never by cooling. Due to this special behavior it was possible to cool single crystals to 90 K. The data collected from such supercooled crystals resulted in a more precise and reliable structure refinement. Interesting structural details of the sterically overcrowded molecule are elucidated. The temperature dependence of the distortions of the nonplanar dimethylamino groups indicates dynamic behavior rather than static disorder.

Out-of-Plane and in-Plane Conduction in Insulating and Strongly Underdoped Cuprates

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3203-3206
Author(s):  
C. C. Almasan ◽  
G. A. Levin ◽  
E. Cimpoiasu ◽  
T. Stein ◽  
D. A. Gajewski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Normal State ◽  
Low Temperatures ◽  
Elementary Step ◽  
Charge Carriers ◽  
Two Dimensional ◽  
Out Of Plane ◽  
Underdoped Cuprates

We report measurements of out-of-plane (ρ c ) and in-plane (ρab) normal-state resistivities of single crystals of insulating PrBa2Cu3O 7-δ and strongly underdoped oxygen deficient YBa2Cu3O 6.41 using a flux transformer method. In the superconducting specimens, the onset of superconductivity was suppressed by a magnetic field of 9 T. We have found that the anisotropy ρc/ρab of these samples increases monotonically at low temperatures with no signs of saturation. The temperature dependence of ρc/ρab for YBa2Cu3O6.41 is well described by ρc/ρab=a +bT-2/3, but over a smaller temperature range than for insulating PrBa2Cu3O 7-δ. Both the absence of saturation of ρc/ρab and its T-2/3 dependence indicate two-dimensional conduction. This means that the average in-plane hopping distance of the localized charge carriers increases with decreasing T according to Mott's [Formula: see text] law, while the elementary step in the c-direction remains T independent, equal to the spacing between the bilayers.

Polarized Raman Scattering Study of ZnGeP2 Single Crystals

1997 ◽  
Vol 484 ◽  
Author(s):  
Spirit Tlali ◽  
Howard E. Jackson ◽  
M. C. Ohmer ◽  
P. G. Schunemann ◽  
T. M. Pollak
Keyword(s):  
Raman Scattering ◽  
Single Crystals ◽  
Raman Spectra ◽  
Low Temperatures ◽  
High Quality ◽  
Crystal Orientations ◽  
Gradient Technique ◽  
Theoretical Predictions ◽  
Scattering Study ◽  
Polarized Raman

AbstractRaman scattering experiments on high quality ZnGeP2 single crystals grown by the seeded horizontal dynamic gradient technique have been carried out. Polarized Raman spectra were obtained in the backscattering geometry at both room and low temperatures for several crystal orientations and compared with group theoretical predictions. Raman spectra from as-grown and annealed samples display distinctive differences which were explored by utilizing two different excitation wavelengths: 514.3 nm and 632.8 nm; the observed differences are attributed to a surface interdiffuasion effect.

scholarly journals Temperature Dependence of Raman-Active Modes of TlIn(0.95Se0.05)2 Single Crystals

2019 ◽  
Vol 64 (2) ◽  
pp. 173
Author(s):  
O. O. Gomonnai ◽  
M. Ludemann ◽  
A. V. Gomonnai ◽  
I. Yu. Roman ◽  
A. G. Slivka ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Phase Transformations ◽  
Single Crystals ◽  
Raman Spectra ◽  
Temperature Interval ◽  
Half Width ◽  
Vibrational Band ◽  
Temperature Behavior ◽  
Frequency Interval ◽  
Temperature Range

The unpolarized Raman spectra of TlIn(S0.95Se0.05)2 single crystals in the frequency interval 16–340 cm−1 are studied in the temperature interval 30 ≤ T ≤ 293 K. The Raman spectra are analyzed by a multipeak simulation using Lorentzian contours. The temperature behavior of the vibrational band parameters (half-width, intensity, and frequency) is studied with the emphasis on the temperature range, where changes related to phase transformations are revealed.

PHOTOCONDUCTIVITY IN CUPROUS OXIDE SINGLE CRYSTALS

1962 ◽  
Vol 40 (12) ◽  
pp. 1703-1713 ◽  
Author(s):  
Emery Fortin ◽  
Frank L. Weichman
Keyword(s):  
Temperature Dependence ◽  
Single Crystals ◽  
Cuprous Oxide ◽  
Low Temperatures ◽  
Surface Recombination ◽  
High Resistivity ◽  
Material Surface ◽  
Conductivity Measurements ◽  
Small Temperature ◽  
Significant Difference

Measurements were made on both single and multicrystalline samples of Cu2O of high resistivity. Conductivity measurements gave three activation energies, 1.0, 0.5, and 0.027 ev, for different temperature regions. The photoconductivity at constant temperatures as a function of wavelength as well as the photoconductivity as a function of temperature at constant wavelengths were measured. Over the temperature range investigated no significant difference was found between single and multicrystalline material. Surface recombination states are postulated to explain the very small temperature dependence at low temperatures.

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