Partial photoneutron reaction cross sections data for 63,65Cu and 80

PARTIAL PHOTONEUTRON REACTION CROSS SECTIONS DATA FOR ^63,65Cu AND ⁸⁰Se RELIABILITY
V.V. Varlamov¹, A.I. Davydov², M.A. Makarov², V.N. Orlin¹, N.N. Peskov¹, M.E. Stepanov<sup>2

1</sup>Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University,

²Physics Faculty of Lomonosov Moscow State University, Moscow, Russia

E-mail: [e-mail]

Experimental data on photodisintegration of a large number of medium and heavy nuclei (^91,94,96Zr, ¹¹⁵In, ^112–124Sn, ¹⁵⁹Tb, ¹⁸¹Ta, ¹⁹⁷Au, ²⁰⁸Pb) obtained primarily at Livermore (USA) and Saclay (France) using quasimonoenergetic annihilation photons and the neutron multiplicity sorting based on its energy measurement were analyzed in [1–3]. It was shown that many data under do not satisfy to proposed objective data reliability criteria: in various energy ranges of initial photons the ratios F₂ = (, 2n)/(, xn) = (, 2n)/[(, 1n) + 2(, 2n) + 3(, 3n) + …] have physically unreliable values larger 0.50 and at the same time ratios F₁ = (, 1n)/(, xn) have physically forbidden negative values. That means that experimental neutron multiplicity sorting has been done erroneously because of large systematic uncertainties. A very noticeable disagreements between experimental and physical criteria based cross section energy dependences were found out for ¹⁵⁹Tb, ¹¹⁶Sn, ⁹⁴Zr, ⁶⁵Cu, ⁸⁰Se.

Therefore new data free of systematic uncertainties under discussion were evaluated for two isotopes ^63,65Cu [4] data obtained at Livermore and ⁸⁰Se [5] data obtained at Saclay. New experimentally–theoretical method [2] was used for evaluation: – ^eval(, in) = F^theor_i ^exp(, xn). It means that competition between partial reactions is in accordance with combined model of photonuclear reactions [6, 7] and their sum ^eval(, xn) is equal to ^exp(, xn) free from neutron multiplicity sorting problems mentioned above.

New cross sections were evaluated for (, 1n) and (, 2n) reactions for isotopes ^63,65Cu and ⁸⁰Se. Using evaluated partial reactions cross sections new data for total photoneutron reaction (, Sn) = [(, 1n) + ( ,2n) + (, 3n) + …] were obtained also. Large deviations of evaluated partial reactions cross sections from experimental ones are discussed in details. It is shown that those deviations are the results of unreliable and erroneous redistribution of many neutrons between the channels with multiplicities “1” and “2”.

The work is partially supported by the RFBR Grant 13–02–00124.

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