Reaction mechanisms of fast neutrons on stable Mo isotopes below 21 MeV

Journal Article · Fri Apr 01 04:00:00 EST 2005 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PhysRevC.71.044617· OSTI ID:20696089

Reimer, P ^[1]; Avrigeanu, V; Glodariu, T ^[2]; Chuvaev, S V; Filatenkov, A A ^[3]; Koning, A ^[4]; Plompen, A J.M.; Weigmann, H ^[1]; Qaim, S M ^[5]; Smith, D L ^[6]

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1. European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg, B-2440 Geel (Belgium)
2. 'Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania)
3. V.G. Khlopin Radium Institute, 2nd Murinski Avenue 28, St. Petersburg 194021 (Russian Federation)
4. Nuclear Research and Consultancy Group, P.O. Box 25, NL-1755 ZG Petten (Netherlands)
5. Institut fuer Nuklearchemie, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)
6. Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

A large number of new measurements with the activation technique were performed for (n,2n) and neutron-induced {delta}Z=1,2 reaction cross sections on the stable molybdenum isotopes in the energy range from 13.5 to 21 MeV. First results were obtained for the {sup 92}Mo(n,2n){sup 91}Mo{sup m},{sup 92}Mo(n,{alpha}){sup 89}Zr{sup m},{sup 94}Mo(n,2n){sup 93}Mo{sup m},{sup 95}Mo(n,p= ){sup 95}Nb{sup m},{sup 96}Mo(n,p) {sup 96}Nb,{sup 96}Mo(n,x){sup 95}Nb{sup m}, {sup 97}Mo(n,p){sup 97}Nb, {sup 97}Mo(n,p){sup 97}Nb{sup m}, {sup 97}Mo(n,x){sup 96}Nb, {sup 98}Mo(n,p){sup 98}Nb{sup m}, {sup 98}Mo(n,x){sup 97}Nb, {sup 98}Mo(n,x){sup 97}Nb{sup m}, and {sup 100}Mo(n,{alpha}){sup 97}Zr reactions, above 16 MeV. A significant number of high-accuracy 14 MeV measurements were performed which are in good agreement with the measurements above 16 MeV for reactions studied in both energy ranges. The rather complete database for the molybdenum isotopes was analyzed with two different sets of consistent model calculations: a local and a global approach. The global approach (a blind calculation with the TALYS code) provides a good overall description of the dominant reaction channels, although the (n,{alpha}) reactions for the heavy isotopes are overpredicted. The local approach (an adjusted calculation with the STAPRE-H code) describes the shapes and magnitudes of the excitation functions well from the reaction thresholds up to 21 MeV using a consistent parameter set, which was optimized based on all experimental information for the nuclei at hand and their immediate neighbors. The agreement between experimental and calculated data is, in general, good both at the maxima and at the tails of the excitation functions, and both for total activation cross sections of a particular channel and for cross sections leading to isomers, showing the viability of the level densities, the optical models, and the {gamma} widths. Comparison of the two model calculations with the data indicates the relevance of an appropriate treatment for preequilibrium (PE) {alpha}-particle emission for the description of the data above 14 MeV. Comparison between the model calculations shows largely different PE deuteron emission contributions to the total ({delta}Z=1,{delta}A=1) cross sections with an additional marked difference in energy dependence. This suggests that emission spectra around 20 MeV are required to establish the magnitude of the PE deuteron emission contribution to this process. New {gamma}-ray strength functions were established by verification against average (n,{gamma}) data and were demonstrated to give good agreement with the measured isomer production cross sections.

• OSTI ID: 20696089
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 4 Vol. 71; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA PARTICLES
COMPARATIVE EVALUATIONS
DEUTERONS
EMISSION SPECTRA
ENERGY DEPENDENCE
ENERGY LEVELS
ENERGY-LEVEL DENSITY
ENERGY-LEVEL TRANSITIONS
EXCITATION FUNCTIONS
FAST NEUTRONS
GAMMA RADIATION
HAUSER-FESHBACH THEORY
MEV RANGE
MOLYBDENUM 100 TARGET
MOLYBDENUM 92 TARGET
MOLYBDENUM 94 TARGET
MOLYBDENUM 95 TARGET
MOLYBDENUM 98 TARGET
NIOBIUM 96
NIOBIUM 97
NUCLEAR REACTION KINETICS
OPTICAL MODELS
STRENGTH FUNCTIONS
ZIRCONIUM 97