Thresholds for Several Photo-Nuclear Reactions

McElhinney, John; Hanson, A. O.; Becker, Robert A.; Duffield, R.B.; Diven, B.C.

doi:10.1103/physrev.75.542

Cited by 100 publications

(8 citation statements)

References 23 publications

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“…Other experiments [15][16][17] have shown the expected decrease of resonance energy with increasing Z. One feature in our results may also indicate this.…”

Section: Discussionsupporting

confidence: 83%

“…It seems possible that with increasing Z the resonance energy has fallen below the 17.6-Mev line giving rise to a decrease in the yield at that energy, whereas the yield averaged over the betatron spectrum continues to increase in about the same manner as for lighter nuclei, more-or-less independently of the location of the resonance. Because of the observed low value of the resonance energy 5 - 16 in Ta, one is not surprised to find that Ta also yields a low cross-section value for the Li spectrum.…”

Section: Discussionmentioning

confidence: 99%

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Neutron Yields from Photo-Disintegration by Gamma-Rays from Lithium

1950

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STEARNSThe relative neutron yield of 33 elements has been studied using the gamma-ray spectrum which arises from proton bombardment of Li. The samples which were to be irradiated were placed in a block of paraffin. The neutrons were detected using four boron trifluoride proportional counters. Absolute gamma-ray and neutron intensity measurements yielded the value (0.055±0.012) barn for the (y,n) cross section of copper. Rough indications were also obtained concerning the relative neutron energy distribution from the samples.

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“…Other experiments [15][16][17] have shown the expected decrease of resonance energy with increasing Z. One feature in our results may also indicate this.…”

Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Neutron Yields from Photo-Disintegration by Gamma-Rays from Lithium

1950

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“…Some evidence for the existence of an effect on El transitions arising from the collective motion of neutrons and protons can be drawn from the existence of the giant resonances in photoemission cross sections [19][20][21][22][23][24][25] which occur at 15-25 Mev excitation of the product nucleus. These resonances have been interpreted by Goldhaber and Teller 26 as due to the relative vibration of two interpenetrating spheres containing separately the neutrons and protons.…”

Section: Inhibition Of El Transitionsmentioning

confidence: 98%

Isotopic Spin Selection Rule for Electric Dipole Transitions

MacDonald

1955

Phys. Rev.

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The validity of the isotopic spin quantum number in nuclei provides a selection rule on electric dipole transitions. The extent to which this selection rule is violated provides a means of experimentally determining the isotopic spin impurity of nuclear states providing that the radiation widths for uninhibited El radiation can be predicted. The sources of possible variations of El matrix elements are discussed with reference to the reliability of predicted El radiation widths in nuclei for A <20 and excitation energy ^15 Mev. Higher order corrections to the El selection rules are determined and found to be negligible compared to the effects of isotopic spin impurity. It is concluded that the isotopic spin selection rule on El transitions provides a sensitive test of charge independence. Isotopic spin impurity determined in this way can be attributed solely to the Coulomb potential.

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“…In the nonrelativistic approximation only the time component of p gives an appreciable result and since qt=0, q in the numerator becomes zero since it is to be compared with If, while in the denominator where it occurs with n 2 , q 2 = -Q 2 . Since p 3 …”

Section: +P 1 X(l-y)+pxyj+l-qh(l--x)+^(l-x)2}mentioning

confidence: 99%

“…The remainder is the mesonic field correction to neutron-proton scattering. 3 The final cross section will be: (1)…”

Section: Introductionmentioning

confidence: 99%

Field Corrections to Neutron-Proton Scattering in a New Mixed Meson Theory

Beard

Bethe

1951

Phys. Rev.

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The principal relativistic correction to neutron-proton scattering has been computed to fourth order for nonrelativistic energies by calculating the matrix elements using the Feynman method and then subtracting off the appropriate order Born approximation to the Yukawa potential. A new meson theory was used, namely a mixture of pseudovector mesons and pseudoscalar mesons with pseudovector coupling; it is shown that by suitable choice of the coupling constants the divergent terms could be eliminated in all orders (disregarding possible electromagnetic couplings). The mesonic field corrections to neutron-proton scattering were found to be of order fi/M smaller than the static Yukawa potential cross section; in practical applications, they could be treated as a perturbing potential to the static Yukawa interaction.

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Thresholds for Several Photo-Nuclear Reactions

Cited by 100 publications

References 23 publications

Neutron Yields from Photo-Disintegration by Gamma-Rays from Lithium

Neutron Yields from Photo-Disintegration by Gamma-Rays from Lithium

Isotopic Spin Selection Rule for Electric Dipole Transitions

Field Corrections to Neutron-Proton Scattering in a New Mixed Meson Theory

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