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Title: Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 191}Ir

Abstract

The {sup 191}Ir(n,2n){sup 190}Ir cross section was measured by means of the activation technique at four neutron energies in the range 10.0-11.3 MeV. The quasimonoenergetic neutron beam was produced via the {sup 2}H(d,n){sup 3}He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR 'Demokritos'. The cross section for the population of the second high spin (11{sup -}) isomeric state was measured along with the sum of the reaction cross section populating both the ground (4{sup -}) and the first isomeric state (1{sup -}). Statistical model calculations taking into account pre-equilibrium emission were performed and compared with all the available experimental data. The experimentally deduced excitation function for populating both the ground and first isomeric state was well reproduced by the theoretical calculations. The statistical model calculations of populating the second metastable state revealed its strong dependence on the details of the introduced level scheme, as well as on the ratio between the effective moment of inertia and the rigid body moment of inertia of the residual nucleus. The experimental cross-section data corresponding to the second isomeric state and to the isomeric ratio were reproduced in a quite consistent way by the calculations.

Authors:
; ; ; ; ; ; ;  [1];  [2]
  1. Department of Physics, National Technical University of Athens, Athens (Greece)
  2. (Greece)
Publication Date:
OSTI Identifier:
20995139
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.034607; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; DEUTERIUM; EXCITATION FUNCTIONS; HELIUM 3; IRIDIUM 190; IRIDIUM 191; ISOMER RATIO; METASTABLE STATES; MEV RANGE 10-100; MOMENT OF INERTIA; NCSR; NEUTRON BEAMS; NEUTRONS; SPIN; STATISTICAL MODELS; VAN DE GRAAFF ACCELERATORS

Citation Formats

Patronis, N., Papadopoulos, C. T., Galanopoulos, S., Kokkoris, M., Perdikakis, G., Vlastou, R., Lagoyannis, A., Harissopulos, S., and Institute of Nuclear Physics, NCSR 'Demokritos', Athens. Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 191}Ir. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.034607.
Patronis, N., Papadopoulos, C. T., Galanopoulos, S., Kokkoris, M., Perdikakis, G., Vlastou, R., Lagoyannis, A., Harissopulos, S., & Institute of Nuclear Physics, NCSR 'Demokritos', Athens. Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 191}Ir. United States. doi:10.1103/PHYSREVC.75.034607.
Patronis, N., Papadopoulos, C. T., Galanopoulos, S., Kokkoris, M., Perdikakis, G., Vlastou, R., Lagoyannis, A., Harissopulos, S., and Institute of Nuclear Physics, NCSR 'Demokritos', Athens. Thu . "Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 191}Ir". United States. doi:10.1103/PHYSREVC.75.034607.
@article{osti_20995139,
title = {Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 191}Ir},
author = {Patronis, N. and Papadopoulos, C. T. and Galanopoulos, S. and Kokkoris, M. and Perdikakis, G. and Vlastou, R. and Lagoyannis, A. and Harissopulos, S. and Institute of Nuclear Physics, NCSR 'Demokritos', Athens},
abstractNote = {The {sup 191}Ir(n,2n){sup 190}Ir cross section was measured by means of the activation technique at four neutron energies in the range 10.0-11.3 MeV. The quasimonoenergetic neutron beam was produced via the {sup 2}H(d,n){sup 3}He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR 'Demokritos'. The cross section for the population of the second high spin (11{sup -}) isomeric state was measured along with the sum of the reaction cross section populating both the ground (4{sup -}) and the first isomeric state (1{sup -}). Statistical model calculations taking into account pre-equilibrium emission were performed and compared with all the available experimental data. The experimentally deduced excitation function for populating both the ground and first isomeric state was well reproduced by the theoretical calculations. The statistical model calculations of populating the second metastable state revealed its strong dependence on the details of the introduced level scheme, as well as on the ratio between the effective moment of inertia and the rigid body moment of inertia of the residual nucleus. The experimental cross-section data corresponding to the second isomeric state and to the isomeric ratio were reproduced in a quite consistent way by the calculations.},
doi = {10.1103/PHYSREVC.75.034607},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • It has been shown that on the basis of the Hauser-Feshbach theory, and taking into account the law of the conservation of moment, the isomer ratio for the reaction /sup 237/Np (n, 2n) can be calculated. The indeterminateness of the modeling of the /sup 236/Np level scheme, to all appearances, has little effect on the energy dependence of the isomeric ratio. The error in the calculated cross section for the (n, 2n) reaction is determined chiefly by the error in the experimental data on the isomeric ratio and on the cross section for the formation of the short-lived state. Obtainingmore » a correct estimate of the error is made difficult by the scarcity of experimental data on the isomeric ratio. The results of this work can be useful in practical activity when combined with an estimate of the cross sections and the creation of a complete system of neutron cross sections for /sup 237/Np. Theoretical estimates of the cross sections can to a significant extent compensate for the scarcity and indeterminateness of the experimental data.« less
  • The isomeric cross section ratio {sigma}{sub m}/{sigma}{sub g} for the reaction {sup 45}Sc(n,2n) {sup 44}Sc{sup m,g} was measured in the neutron energy range of 13.6{endash}14.9 MeV for six different neutron energies. The neutrons were produced by the {sup 3}H(d,n){sup 4}He reaction utilizing a SAMES T-400 neutron generator. Isomeric cross section ratios were determined by applying the method of least squares to the time behavior of the ground-state decay of isomeric pair. The absolute cross section for the formation of the metastable state was measured by the usual activation technique. The ground-state cross section was then obtained by using the absolutemore » cross section of the metastable state and isomeric cross section ratio for each neutron energy. Experimental cross section values and isomeric cross section ratios were compared with those obtained by a statistical model calculation. {copyright} {ital 1997} {ital The American Physical Society}« less