Radiative capture cross sections of tellurium isotopes as a function of neutron energies up to 1.5 keV

The radiative capture cross sections of tellurium isotopes have been measured as a function of neutron energies up to 1.5 keV. The values of ₀ and of the spin levels, as well as _n ⁰/D have been found for the even-odd isotopes Te¹²³ and Te¹²⁵.Translated from Atomnaya Énergiya, Vol. 14, No. 3, pp. 264–272, March, 1963.This is the second of a series of papers on the neutron cross sections of separated isotopes (for the first paper, on molybdenum isotopes, see ZhÉTP44, No. 4 (1963).     

Cobalt cross sections for 14 MeV neutrons

14 MeV cross sections for the reactions ⁵⁹Co(n,2n) ^58m+gCo, ⁵⁹Co(n,p) ⁵⁹Fe and ⁵⁹Co(n,) ⁵⁶Mn were measured relative to the ⁵⁶Fe(n,p) ⁵⁶Mn reaction employing the activation technique. Accuracies of about 1% were achieved for the (n,) reaction and 2% for the others. The isomeric cross section ratio was measured for the ⁵⁹Co(n,2n) reactions.

Nuclear reactions – ⁵⁹Co(n,2n) ^58m+gCo, ⁵⁹Co(n,p) ⁵⁹Fe, ⁵⁹Co(n,) ⁵⁶Mn, E_n = 14.3, 14.7 MeV: measured activation cross sections relative to ⁵⁶Fe(n,p) ⁵⁶Mn.

⁵⁹Co(n,2n) ^58m,gCo, E_n = 14.3 MeV; measured isomeric cross section ratio. Natural targets. Ge, NaI and 4πβ detectors.     

Theoretical electron-atom elastic scattering cross sections: Selected elements, 1 keV to 256 keV

Calculated differential elastic electron scattering cross sections for 24 selected elements are presented in tabular form in the energy range 1 to 256 keV at values of 2ⁿ keV. The total elastic and momentum-transfer cross sections are tabulated also. Parameters for 12-parameter analytic fits to the differential values are given for 80 elements in a second table. The calculations were done in the relativistic static approximation with relativistic atomic wavefunctions for the heavier elements (Z > 35).     

Isoelectronic sequence fits to configuration-averaged photoionization cross sections and ionization energies

Hartree-Fock wave functions have been used to calculate configuration-averaged photonization cross sections and ionization energies for orbitals 1s ⩽ nl ⩽ 5g in He-like through Al-like isoelectronic sequences. The photoionization cross sections have been fitted as a function of the nuclear charge, Z, and photon energy, X, in threshold units, with average error of less than 10%. The ionization energies have been fitted as a function of Z with errors of less than 0.5%.     

Effective cross sections for fission of U233, U235, Pu239 and Pu240 by neutrons with energies from 30 kev to 5 Mev

Measurements have been made of the absolute values of the effective fission cross sections in U²³³, U²³⁵, Pu²³⁹ and Pu²⁴⁰, using as photoneutron sources Sb + Be ( 30 kev), Na + D₂O ( 250 kev), Na + Be ( 900 kev), a source with a simulated fission-neutron spectrum and Po--Be. The fission cross sections for 30 kev-neutrons are 3.06 ± 0.16, 2.21 ± 0.12 and 1.79 ± 0.11 barns for U²³³, U²³⁵ and Pu²³⁹, respectively. As the neutron energy Is increased from 30 kev to 250 kev the cross sections in U²³³ and U²³⁵ fall off by approximately 35% and then remain almost constant while the cross section in Pu²³⁹ falls off by 12% and then increases. The effective cross sections for fission in Pu²⁴⁰ for 900-kev and 5-Mev neutrons is 1.4 barns and the threshold for fission in Pu²⁴⁰ lies within the limits 250 and 900 kev.In conclusion the authors wish to express their gratitude to P. E. Spivak for help in formulating the problem and a discussion of the results.