Lattice frequency spectra of Pb and Pb40Tl60 by neutron spectrometry

1970 ◽  
Vol 48 (15) ◽  
pp. 1781-1788 ◽  
Author(s):  
A. P. Roy ◽  
B. N. Brockhouse
Keyword(s):  
Force Constant ◽  
Direct Evidence ◽  
Coherent Scattering ◽  
Neutron Spectrometry ◽  
Frequency Spectra ◽  
Polycrystalline Specimen ◽  
Lattice Frequency ◽  
Slow Neutrons

Lattice frequency spectra of Pb and Pb40Tl60 have been measured at 90 °K by inelastic coherent scattering of slow neutrons from a polycrystalline specimen. The results compare favorably with the tunneling measurements of Rowell, McMillan, and Feldman. In Pb40Tl60 we see direct evidence of energy smearing arising from the finite lifetimes of the phonons caused by force-constant disorder in the alloy.

scholarly journals The scattering of slow neutrons by ortho - and para -hydrogen

1955 ◽  
Vol 230 (1180) ◽  
pp. 19-32 ◽  
Keyword(s):  
Scattering Amplitudes ◽  
Cross Section ◽  
Cross Sections ◽  
Scattering Amplitude ◽  
Coherent Scattering ◽  
Para Hydrogen ◽  
Cavendish Laboratory ◽  
Proton Interaction ◽  
Scattering Cross Sections ◽  
Slow Neutrons

The neutron velocity selector of the Cavendish Laboratory has been used to measure the scattering cross-sections of ortho- and para -hydrogen for slow neutrons. The triplet and singlet scattering amplitudes of the neutron-proton interaction may be deduced from these cross-sections. The values obtained are a t = (0·537 ± 0·004) x 10 -12 cm, a s = -(2·373 ±0·007) x 10 -12 cm, where a t and a s are the triplet and singlet scattering amplitudes respectively. The values of the coherent scattering amplitude ƒ = 2(3/4 a +1/4 a ), and of the free proton cross-section σ ƒ = 4π(3/4 a 2 t + 1/4 a 2 s given by the above values of a t and a s , are ƒ = -(0·380 ± 0·005) x 10 -12 cm, σ ƒ = (20·41 ± 0·14) x 10 -24 cm 2 .

Amplituden für kohärente Neutronen-Streuung gemessen an chemischen Verbindungen / Coherent Neutron Scattering Amplitudes Obtained from Chemical Compounds

1972 ◽  
Vol 27 (6) ◽  
pp. 901-905 ◽  
Author(s):  
L. Koester ◽  
K. Knopf
Keyword(s):  
Scattering Amplitudes ◽  
Neutron Scattering ◽  
Small Angle ◽  
Good Accuracy ◽  
Chemical Compounds ◽  
Coherent Scattering ◽  
Small Angle Scattering ◽  
Angle Scattering ◽  
Slow Neutrons

Abstract Coherent Neutron Scattering Amplitudes Obtained from Chemical Compounds Utilizing the small angle scattering of slow neutrons by Christiansen-filters we could determine with a good accuracy the scattering amplitudes of powders by comparing with wellknown liquids. Investigations on powders of halides and sulfates yielded coherent scattering amplitudes of the bound atoms (in 10-13 cm) : a (Na) = 3.63 ±0.02; a(K) =3.71 ±0.02; a (Rb) =7.08 ± 0.02; a (Cs) = 5.42 ± 0.02; a(Tl) =8.89 ±0.02; a (Br) =6.77 ±0.02; and a (I) =5.28 ±0.02. The scattering amplitudes of the liquids and the elements as standards are based on directly determined amplitudes from gravity-mirror measurements.

Kohn Anomaly and Coherent Scattering of Slow Neutrons in Liquid Metals

1965 ◽  
Vol 15 (17) ◽  
pp. 693-694
Author(s):  
K. S. Singwi ◽  
Lars-Erik Andersson
Keyword(s):  
Liquid Metals ◽  
Coherent Scattering ◽  
Slow Neutrons

Coherent scattering of slow neutrons by liquid argon

Physica ◽  
1965 ◽  
Vol 31 (8) ◽  
pp. 1257-1285 ◽  
Author(s):  
K.S. Singwi
Keyword(s):  
Coherent Scattering ◽  
Liquid Argon ◽  
Slow Neutrons

Coherent Scattering of Slow Neutrons by a Liquid

1964 ◽  
Vol 136 (4A) ◽  
pp. A969-A980 ◽  
Author(s):  
K. S. Singwi
Keyword(s):  
Coherent Scattering ◽  
Slow Neutrons

Crystal Structure Determination of Glycerol-Containing Lipids from Electron Diffraction Data. Use of Analog Compounds Based upon Configurational Isomers of Cyclopentane-1, 2, 3-TRIOL

1977 ◽  
Vol 35 ◽  
pp. 24-25
Author(s):  
Douglas L. Dorset ◽  
Anthony J. Hancock
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Surface ◽  
Coherent Scattering ◽  
Crystal Structure Determination ◽  
Electron Diffraction Data ◽  
Polar Group ◽  
Axis Orientation

Lipids containing long polymethylene chains were among the first compounds subjected to electron diffraction structure analysis. It was only recently realized, however, that various distortions of thin lipid microcrystal plates, e.g. bends, polar group and methyl end plane disorders, etc. (1-3), restrict coherent scattering to the methylene subcell alone, particularly if undistorted molecular layers have well-defined end planes. Thus, ab initio crystal structure determination on a given single uncharacterized natural lipid using electron diffraction data can only hope to identify the subcell packing and the chain axis orientation with respect to the crystal surface. In lipids based on glycerol, for example, conformations of long chains and polar groups about the C-C bonds of this moiety still would remain unknown.One possible means of surmounting this difficulty is to investigate structural analogs of the material of interest in conjunction with the natural compound itself. Suitable analogs to the glycerol lipids are compounds based on the three configurational isomers of cyclopentane-1,2,3-triol shown in Fig. 1, in which three rotameric forms of the natural glycerol derivatives are fixed by the ring structure (4-7).

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