PHOTONEUTRON CROSS SECTIONS OF SOME ELEMENTS

1954 ◽  
Vol 32 (1) ◽  
pp. 49-59 ◽  
Author(s):  
J. Goldemberg ◽  
Leon Katz
Keyword(s):  
Statistical Theory ◽  
Cross Sections ◽  
Neutron Yield ◽  
Preceding Paper ◽  
Maximum Energy ◽  
Experimental Results ◽  
Sum Rule ◽  
Data Support ◽  
The University ◽  
Good Agreement

The neutron yield from photo-reactions in nine elements has been measured as a function of the maximum energy of the University of Saskatchewan Betatron. Cross sections are given for each of the reactions as calculated from these data. The integrated cross sections are compared with theoretical sum-rule predictions of Levinger and Bethe and good agreement is obtained with x = ½. The data support the conclusions reached in a preceding paper by Montalbetti, Katz, and Goldemberg. The competition between (γ, n) and (γ, p) reactions in chromium and in nickel is analyzed in the light of these experimental results. Good agreement with statistical theory is obtained in both cases.

L X-ray fluorescence cross sections in the atomic region 59 ≤ Z ≤ 82 excited by 16.58 keV photons

1996 ◽  
Vol 74 (5-6) ◽  
pp. 230-235 ◽  
Author(s):  
D. V. Rao ◽  
R. Cesareo ◽  
G. E. Gigante
Keyword(s):  
Excitation Energy ◽  
Least Squares ◽  
Cross Sections ◽  
Experimental Results ◽  
X Ray ◽  
Experimental Cross ◽  
Average Fluorescence ◽  
Good Agreement

LL, Lα, Lβ, and Lγ X-ray fluorescence cross sections for Pr, Sm, Gd, Dy, Ho, Er, Yb, Pt Au, and Pb were measured at the excitation energy 16.58 keV. An X-ray tube and a secondary excitor system was used instead of radioisotopes for the measurements. Experimental cross sections are compared with the theoretical estimates based on relativistic Dirac–Hartree–Slater theory. Average L-shell fluorescence yields [Formula: see text] are deduced using the present experimental cross sections and the theoretical subshell photoionization cross sections. The derived average fluorescence yields are fitted by least squares to polynomials in Z of the form ΣnanZn and compared with theoretical and earlier fitted values. Good agreement is observed ' between the experimental results and the theoretical estimates based on relativistic Dirac–Hartree–Slater theory.

scholarly journals CROSS-SECTIONS FOR PHOTONUCLEAR REACTIONS 93Nb(γ,n)92mNb AND 93Nb(γ,n)92tNb IN THE END-POINT BREMSSTRAHLUNG ENERGIES 36...91 MeV

2020 ◽  
pp. 148-153
Author(s):  
A.N. Vodin ◽  
O.S. Deiev ◽  
I.S. Timchenko ◽  
S.N. Olejnik ◽  
A.S. Kachan ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Bremsstrahlung Spectrum ◽  
Photonuclear Reactions ◽  
End Point ◽  
Γ Ray ◽  
First Time ◽  
Good Agreement

The flux-weighted averaged over the energy range of bremsstrahlung spectrum from reaction threshold up to the maximum energy of γ-ray cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb photonuclear reactions were determined by the gamma-activation method within the end-point bremsstrahlung energies Еmax = 36…91 MeV. Activation of 93Nb targets has been done by a bremsstrahlung flux using an electron beam at the linear accelerator LUE-40 at RDC "Accelerator" NSC KIPT. The γ-ray spectra of irradiated targets were registered using the HPGe detector with an energy resolution of 1.8 keV for the 1332 keV line 60Co. To control the bremsstrahlung flux we used natMo witness-targets and a reaction cross-section of 100Mo(γ,n)99Mo. Obtained experimental cross-sections <σ(E)> of the studied reactions are in good agreement with the theoretical values calculated within TALYS 1.9 code and the results of other authors. The averaged cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb reactions in the energy range 35...45 MeV and > 70 MeV were obtained for the first time.

scholarly journals The Electron Impact Ionization Cross Sections of Methanol, Ethanol and 1-Propanol

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 60 ◽  
Author(s):  
Yogesh Kumar ◽  
Manoj Kumar ◽  
Sachin Kumar ◽  
Rajeev Kumar
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Impact Ionization ◽  
Experimental Results ◽  
Oscillator Strengths ◽  
Ionization Cross ◽  
Total Ionization ◽  
Plane Wave Born Approximation ◽  
Ionization Cross Sections ◽  
Good Agreement

In the present investigation, the plane-wave Born approximation was employed to calculate the total ionization cross sections by electron impact of methanol, ethanol and 1-propanol from the threshold of ionization to 10 MeV. This method requires continuum generalized oscillator strengths (CGOSs). The two different semi-phenomenological expressions of CGOS, given by Mayol and Salvat and Weizsacker and Williams, along with approximated form of the continuum optical oscillator strength (COOS) by Khare et al. were used. Furthermore, the average of the above two CGOSs was also used. The calculated ionization cross sections were compared to the available previous theoretical results and experimental data. Out of three CGOSs, the present results with the average CGOS were found in good agreement with the available experimental results for all the considered molecules. Collision parameters CRP were also calculated from 0.1 to 100 MeV and the calculations were found to be in excellent agreement with the experimental results of Reike and Prepejchal.

The Scattering of Positrons by Helium: Total Cross Sections up to 270 eV

1975 ◽  
Vol 53 (10) ◽  
pp. 962-967 ◽  
Author(s):  
B. Jaduszliwer ◽  
A. Nakashima ◽  
D. A. L. Paul
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Reasonable Agreement ◽  
Experimental Results ◽  
Formation Cross Section ◽  
Sum Rule ◽  
Total Cross Sections ◽  
High Energies

The total cross sections for the scattering of positrons by helium have been measured by the method of transmission in the 16 to 270 eV energy range. The experimental results are higher than those of Canter et al. but are in reasonable agreement with recent results of Griffith et al., and at high energies tend towards Born approximation calculations. The integral of the cross section over positron momentum is smaller than the sum rule estimate made by Bransden et al. A tentative value of (0.034 ± 0.017)πa02 is assigned to the positronium formation cross section at threshold.

Many-Electron Correlations in the Photoionization of a Nitrogen Atom

1974 ◽  
Vol 52 (4) ◽  
pp. 349-354 ◽  
Author(s):  
N. A. Cherepkov ◽  
L. V. Chernysheva ◽  
V. Radojević ◽  
I. Pavlin
Keyword(s):  
Nitrogen Atom ◽  
Cross Section ◽  
Cross Sections ◽  
Random Phase Approximation ◽  
Random Phase ◽  
Electron Correlations ◽  
Sum Rule ◽  
Hartree Fock ◽  
The Cross ◽  
Good Agreement

Photoionization cross sections for the outer shell of the nitrogen atom ground state are calculated in the single-particle Hartree–Fock approximation and, in order to take into account many-electron correlations, also in the Random Phase Approximation with Exchange (RPAE). To be able to apply the RPAE, its modification for the half-filled shell atom, such as nitrogen atom, is presented. Calculation of length and velocity forms of the cross section in both approximations are compared with the available experimental data, and a good agreement is obtained. It has been found that in the RPAE the influence of many-electron correlations in a nitrogen atom is not great, but it is very important since, in contrast to the Hartree–Fock approximation, it results in the validity of the sum rule and the coincidence of the length and velocity forms of the cross sections, in agreement with the requirement of the general theory. The angular distribution of photoelectrons is also calculated in the RPAE, which has not been measured so far.

scholarly journals Theory of efficient shell implosions

1989 ◽  
Vol 7 (2) ◽  
pp. 189-205 ◽  
Author(s):  
Masakatsu Murakami ◽  
Katsunobu Nishihara ◽  
Hideaki Takabe
Keyword(s):  
Theoretical Model ◽  
Neutron Yield ◽  
Mass Density ◽  
Coupling Efficiency ◽  
Experimental Results ◽  
Moderate Intensity ◽  
Ion Temperature ◽  
Hollow Shell ◽  
Theoretical Predictions ◽  
Good Agreement

A theoretical model of spherical ablative implosion is presented. The implosion performances such as the target coupling efficiency are estimated from the aspect ratio and initial mass density of a target shell, provided the laser is fixed at moderate intensity for a given wavelength. The model is applied to the experimental results obtained for both plastic hollow shell targets and DT gas-filled GMB targets by use of the twelve-beam green GEKKO XII laser. In addition to the target coupling efficiency, it is shown for the gas-filled targets that the theoretical predictions of neutron yield, ion temperature, and fuel ρ and ρR are in good agreement with the experimental results. Reduction of neutron yields due to irradiation nonuniformity is also discussed, and 5% of absorption nonuniformity is found to be required for explaining the discrepancies in neutron yield between the experiments and the theory.

Sum Rule Photodisintegration Cross Sections of 6Li

1974 ◽  
Vol 52 (3) ◽  
pp. 202-206
Author(s):  
H. L. Yadav ◽  
B. K. Srivastava
Keyword(s):  
Charge Distribution ◽  
Cross Sections ◽  
Sum Rules ◽  
Wave Functions ◽  
Radial Wave ◽  
Sum Rule ◽  
Dependent Potential ◽  
Good Agreement

We apply the sum rules of Levinger and Bethe to calculate the integrated [Formula: see text] cross sections for 6Li using the Gaussian and Irving forms of radial wave functions whose parameters are determined by fitting the r.m.s. radius of charge distribution in 6Li. For the potential in the σint calculation we use the central velocity-dependent potential of Herndon et al. Our results for σint and σb for 6Li show reasonably good agreement with experiments.

scholarly journals DTA measurements in the ternary Ag-Au-Ga system

2020 ◽  
pp. 21-21
Author(s):  
Dominika Jendrzejczyk-Handzlik ◽  
Piotr Handzlik
Keyword(s):  
Experimental Data ◽  
Thermal Analysis ◽  
Phase Diagram ◽  
Differential Thermal Analysis ◽  
Phase Transformations ◽  
Cross Sections ◽  
Calphad Method ◽  
Experimental Results ◽  
Zero Rate ◽  
Good Agreement

In this work, the ternary Ag-Au-Ga system was studied experimentally by differential thermal analysis (DTA). Measurements were carried out along two chosen cross-sections determined by the ratio of mole fractions XAg/XGa=1:1 and XAu/XGa=1:1 by applying Pegasus 404 apparatus form Netzsch. Experiments were performed at three rates: 1 K min-1, 5 K min-1 and 10 K min-1. Next, the obtained experimental results were used to estimate the temperatures of liquidus by applying extrapolation to zero rate. Moreover, the temperatures of invariant reactions and other phase transformations were investigated from DTA measurements which were carried out with the rate 1 K min-1. Finally, the experimental results were compared with the isopleths obtained from prediction and calculation of the phase diagram which were done by using CALPHAD method. Experimental data obtained in this work are in good agreement with the results of calculation.

scholarly journals Cross sections of the 89Y(p,γ) reaction relevant to the p process

2019 ◽  
Vol 11 ◽  
Author(s):  
P. Tsagari ◽  
M. Kokkoris ◽  
E. Skreti ◽  
P. Demetriou ◽  
S. Galanopoulos ◽  
...  
Keyword(s):  
Statistical Theory ◽  
Angular Distribution ◽  
Cross Section ◽  
Cross Sections ◽  
Relative Efficiency ◽  
Reaction Rates ◽  
Hpge Detectors ◽  
The Cross ◽  
Good Agreement

The cross section of the 89Y(p,7)90Zr reaction was determined at Ep=l.4-4.8 MeV via angle-integrated measurements carried out by means of a 4π Nal summing detector as well as via angular distribution measurements using an array of 4 HPGe detectors with 100% relative efficiency. The resulting cross sections vary from 0.5 to 5 mb. Astrophysical S factors and reaction rates have also been derived. A good agreement between the experimental rates and and the predictions of statistical theory has been found.

A comparison of theory and experiment for photo-ionization cross-sections II. Sodium and the alkali metals

1951 ◽  
Vol 208 (1094) ◽  
pp. 418-430 ◽  
Keyword(s):  
Cross Sections ◽  
Alkali Metals ◽  
Line Strength ◽  
Wave Functions ◽  
Experimental Results ◽  
Ionization Cross ◽  
Sum Rule ◽  
The Cross ◽  
Ionization Cross Sections ◽  
Photo Ionization

A summary is given of the results of experimental determinations of the atomic photo-ionization cross-sections of the alkali metals. Detailed calculations on sodium are described, using Hartree-Fock wave functions, and it is shown that the theory is capable of reproducing the main features of the experimental results. A comparison with line-strength calculations is made, and the applicability of sum-rule tests is discussed. The finite minimum which is found experimentally in the cross-sections of certain of the alkali metals is attributed to spin-orbit perturbations of the free-electron wave functions. For caesium and rubidium the theoretical calculation based on this effect is shown to give minima of a magnitude comparable to those of the experimental results. The accuracy of previous calculations on the cross-sections of Ca ll is discussed, use being made of sum-rule tests.

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