The angular distribution of protons projected by fast neutrons

The nature of the interaction between neutron and proton has assumed great importance in modern nuclear theory, since it is now generally assumed that these two particles form the fundamental constituents of all nuclei. Little direct evidence exists, however, as to the nature of this interaction. The stable existence of the deuteron shows that the force between neutron and proton is attractive, and for purposes of calculation a “square hole” potential well has generally been assumed. With this model some success has been obtained* in correlating the magnitudes of a number of experimentally measurable quantities such as ( a ) the binding energy of the deuteron, ( b ) the total cross-section for neutron-proton scattering (Tuve and Hafstad 1936; Amaldi and Fermi 1936 a ), ( c ) the cross-section for photo electric disintegration of the deuteron (Chadwick and Goldhaber 1935), and ( d ) the cross-section for capture of neutrons by protons (Amaldi and Fermi 1936 b ). The interaction is not completely derivable from the above data, since the values of these quantities depend mainly upon r 2 V , where r is the mean radius and V is the depth of the potential hole.

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On the scattering of fast neutrons by protons

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1947.0110 ◽

1947 ◽

Vol 191 (1025) ◽

pp. 195-209 ◽

Cited By ~ 3

Keyword(s):

Angular Distribution ◽

Cross Section ◽

Cosmic Ray ◽

Fast Neutrons ◽

Meson Mass ◽

Nuclear Forces ◽

Total Scattering ◽

Empirical Results ◽

Meson Theory ◽

Total Scattering Cross Section

The features of the scattering of fast neutrons by protons are calculated using the Møller- Rosenfeld version of the meson theory of nuclear forces. The experimental results of Occhialini & Powell are used to check the predicted angular distribution of the scattered particles and to determine the mass of the meson; the meson mass indicated is about 215 electronic masses, which agrees with the mass of cosmic ray mesons. The total scattering cross-section predicted by the theory agrees with the empirical results.

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The determination of the cross sections for the reactions 27 Al( n , α ) and 56 Fe( n , p ) for 14 MeV neutrons by an absolute method

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1966.0127 ◽

1966 ◽

Vol 292 (1429) ◽

pp. 180-192 ◽

Cited By ~ 5

Keyword(s):

Cross Section ◽

Cross Sections ◽

Standard Error ◽

Particle Method ◽

Systematic Errors ◽

Aluminium Foil ◽

The Mean ◽

The Cross ◽

Experimental Values

Measurements of the cross sections for the reactions 27 Al( n , α ) 24 Na and 56 Fe( n, p ) 56 Mn for neutrons of energy 13.5 ± 0.1 MeV have been made by a radioactivation method. The neutron flux was determined by a variant of the 'associated particle’ method, in which the α -particles produced concurrently with the neutrons from the D + T reaction were estimated in terms of the volume of helium which accumulated when they were brought to rest in an aluminium foil. Cross section values obtained at 13.5 MeV were: for 27 Al( n , α ): 118.1 ± 6.0 mb : for 56 Fe( n, p ): 106.7 ± 4.7 mb. The errors quoted include both the standard error on the mean of the experimental values and an estimate of possible residual systematic errors. The excitation functions for both reactions in the energy region 13.5 to 14.8 MeV have also been investigated, in order to provide secondary cross section values over this range of energies. At 14.8 MeV the values found were: 27 Al( n , α )103.6 ± 5.5 mb; 56 Fe( n, p )96.7 ± 4.5 mb.

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Physical analysis of the fleece of sheep for biological purposes. II. Estimation of the number and mean diameter of wool fibres from a cast of their cross-section

Australian Journal of Agricultural Research ◽

10.1071/ar9510195 ◽

1951 ◽

Vol 2 (2) ◽

pp. 195 ◽

Cited By ~ 3

Author(s):

LT Wilson

Keyword(s):

Cross Section ◽

Unit Area ◽

Physical Analysis ◽

Mean Diameter ◽

The Mean ◽

The Cross ◽

Limits Of Error

A technique has been developed for making a cast of the cross-section of a bundle of wool fibres under defined packing conditions. By counting the fibre impressions per unit area in representative portions of the cast, both the total number of fibres and the mean diameter can be rapidly calculated within fairly close limits of error.

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The cross-section and angular distribution of the D-D reactions below 50 keV

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1953.0006 ◽

1953 ◽

Vol 216 (1124) ◽

pp. 57-65 ◽

Cited By ~ 13

Keyword(s):

Angular Distribution ◽

Total Cross Section ◽

Cross Section ◽

Proportional Counter ◽

Angular Distributions ◽

Asymmetry Coefficient ◽

Gas Target ◽

The Asymmetry ◽

The Cross ◽

Bombarding Energy

A thin gas target was used and the particles from the reactions were detected by a proportional counter. The results show that the total cross-section for the two reactions is the same to within 1%, but that the angular distributions of the products are significantly different. The asymmetry coefficient for the reaction D( d , n ) 3 He is given by 0·31 + 0·0058 E , compared with 0·13 + 0·0047 E for reaction D( d , p ) 3 H, where E is the bombarding energy in kilovolts.

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On the cancellation of radiative corrections to the cross section of electron-proton scattering

Physics Letters B ◽

10.1016/j.physletb.2019.06.034 ◽

2019 ◽

Vol 795 ◽

pp. 172-176 ◽

Cited By ~ 1

Author(s):

V.S. Fadin ◽

R.E. Gerasimov

Keyword(s):

Cross Section ◽

Radiative Corrections ◽

Proton Scattering ◽

The Cross

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UPS of a-Si:H: What is the energy of the Er 4f states?

MRS Proceedings ◽

10.1557/proc-609-a11.1 ◽

2000 ◽

Vol 609 ◽

Cited By ~ 1

Author(s):

Leandro R. Tessler ◽

Cínthia Piamonteze ◽

Ana Carola Iniguez ◽

Abner de Siervo ◽

Richard Landers ◽

...

Keyword(s):

Binding Energy ◽

Excitation Energy ◽

Cross Section ◽

Energy Gap ◽

Valence States ◽

Erbium Doped ◽

Order Of Magnitude ◽

Synchrotron Light ◽

The Cross ◽

Er Doped

ABSTRACTOne very important problem concerning erbium-doped silicon is the electronic structure of the Er3+ impurities. In particular, it is still not clear if the 4f levels can be treated as frozen core levels or their overlap with s and p states of their neighbors must be considered explicitly. For crystalline Si, the 4f levels have been supposed to be anywhere between 20 eV below the valence band and within the energy gap. In this paper we report on the first ultraviolet photoemission spectroscopy (UPS) measurements on Er-doped a-Si:H. Samples of a-Si:H<Er> with different Er contents (up to 1 at. % Er) were prepared by co-sputtering from a Si target partially covered with metallic Er platelets. In order to enhance the Er states relative to the Si and H states, the excitation energy was tuned between 40 and 140 eV with a synchrotron light source. At 140 eV excitation energy the cross-section of the Er 4f and 5p states is more than an order of magnitude higher than the cross section of the Si 3s or 3p states. As the Er concentration increases, a shoulder and then a peak appears at 10.0±0.5 eV binding energy. The intensity and width of this peak is well correlated with the Er concentration, and with the Er 5p and 5p½ levels at 26 and 32 eV binding energy, respectively. We attribute the peak at 10.0±0.5 eV binding energy to the Er 4f level. These are the only occupied states that can be related to the presence of Er, indicating that these levels are not valence states and consequently can be treated as frozen core levels.

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On the scattering of fast neutrons by protons

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100022726 ◽

1946 ◽

Vol 42 (1) ◽

pp. 45-54 ◽

Cited By ~ 18

Author(s):

A. Pais

Keyword(s):

Angular Distribution ◽

Total Cross Section ◽

Cross Section ◽

Neutral Theory ◽

High Energy ◽

Fast Neutrons ◽

Neutral Meson ◽

Meson Theory ◽

Charge Dependence ◽

Symmetrical Type

1. Introduction. Recent experiments by Amaldi and his collaborators on the scattering of high-energy neutrons (of 10–15 MeV.) by protons(2) have disclosed a considerable anisotropy in the angular distribution of the scattered particles. Theoretical discussions of this problem show an interesting feature in that the results depend sensitively on the basic assumptions involved with regard to the charge dependence of the neutron-proton interaction. This can be seen in particular from calculations by Rarita and Schwinger(3) and by Ferretti(4). The former authors started from the assumption of a distance dependence of this interaction represented by a square well, while the angular and spin dependence included terms of the axial dipole type. If the charge dependence was further assumed to be of the ‘symmetrical’ type, they found a value for the anisotropy in strong disagreement with experiment, whereas the total cross-section agreed with the measured value; a ‘neutral’ theory, on the other hand, yielded agreement as regards anisotropy, but a total cross-section too large by a factor of the order of 1·5. Ferretti investigated the scattering on Bethe's neutral meson theory(5) and found satisfactory agreement with regard to both angular distribution and total cross-section. It should be stressed that all calculations mentioned were performed in the approximation in which only the contributions of the S- and P-waves are considered.

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The initial dispersion of contaminant in Poiseuille flow and the smoothing of the snout

Journal of Fluid Mechanics ◽

10.1017/s0022112076002279 ◽

1976 ◽

Vol 77 (3) ◽

pp. 593-602 ◽

Cited By ~ 20

Author(s):

P. C. Chatwin

Keyword(s):

Cross Section ◽

Poiseuille Flow ◽

Molecular Diffusion ◽

Lateral Diffusion ◽

Longitudinal Diffusion ◽

Molecular Diffusivity ◽

Discharge Velocity ◽

Smoothing Process ◽

The Mean ◽

The Cross

In Poiseuille flow in a circular tube passive contaminant initially spread uniformly over the cross-section would be pulled out in a paraboloidal snout in the absence of any diffusive mechanism, and there would be a discontinuity in $\overline{C}$, the mean concentration over the cross-section, associated with the contaminant at the front of the snout. In reality molecular diffusion smooths out this snout in two ways: direct longitudinal diffusion and the interaction between lateral diffusion and advection. The effect of these two mechanisms is discussed, and determined for small values of κt/a2, where t is the time since injection, κ is the molecular diffusivity and a is the tube radius. For such values, important in many applications, the tube walls play no part in the smoothing process. It is shown that for $\kappa t/a^2 < 0.25(\overline{u}a/\kappa)^{-\frac{2}{3}}$, where $\overline{u}$ is the discharge velocity, the effect of longitudinal diffusion dominates over that of the interaction, which is, in turn, dominant for $\kappa t/a^2 > 2.5(\overline{u}a/\kappa)^{-\frac{2}{3}}$, when $\overline{C}$ is close to the form described by Lighthill (1966).

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Resonance phenomena in the interaction of fast neutrons with beryllium and aluminium

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1947.0141 ◽

1947 ◽

Vol 192 (1028) ◽

pp. 114-127 ◽

Cited By ~ 19

Keyword(s):

Energy Level ◽

Cross Section ◽

Neutron Energy ◽

Cross Sections ◽

Accurate Determination ◽

Fast Neutrons ◽

Transmission Method ◽

The Cross ◽

Scattering Cross Sections

The total scattering cross-sections of beryllium and aluminium have been measured by a transmission method for neutrons of energies between 0∙35 and 0∙55 MeV and 1∙8 and 4∙0 MeV. Resonances have been found in the scattering by beryllium at a neutron energy of 2∙6 MeV and in the scattering by aluminium at neutron energies of 2∙4 and 2∙9 MeV. It has been shown that the cross-section for the reaction 9 Be ( n , α ) 6 He also has a resonance at 2∙6 MeV, and an accurate determination of the cross-section for this reaction has been made. A discussion is given of the properties of the energy level in 10 Be responsible for the resonances in the case of beryllium.

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