PHOTONUCLEAR REACTION ON MOLYBDENUM ISOTOPES B.S. Ishkhanov, I.M. Kapitonov, A.A. Kuznetsov, V.N. Orlin, Han Dong Yoon, 2014, published in Yadernaya Fizika, 2014, Vol. 77, No. 11, pp. 1427–1435 DOI : 10.1134/S106377881410007X 2015 KPS fall Meeting 2015. 10. 22. Han Dong Yoon Skobeltsyn Institute of Nuclear Physics Faculty of Physics MSU

Outline Introduction Description of experiments Experimental calculation Theoretical Calculation Results Analysis Summary

Diagram example of GDR flow : reaction 92Mo(γ,2n)90Mo Introduction Schematic cross-section of photonuclear reaction σ GDR Nuclear Resonance Fluorescence ≈ 10 МэВ Bn,p 10MeV 100MeV Eγ Diagram example of GDR flow : reaction 92Mo(γ,2n)90Mo γ γ GDR 2n 10-19с γ 10-9 - 10-17s p n γ 90Mo ε /β+ T1/2 = 5.56 h 10-9 - 10-17s 90Nb 92Mo

Description of experiment Electron accelerator RTM-70 pulsed racetrack microtron Bremsstrahlung converter tungsten with 2.5mm thick Target of study : natural mixture of molybdenum 100Mo(9.82%), 98Mo(24.39%), 97Mo(9.60%), 96Mo(16.67%), 95Mo(15.84% ), 94Mo(9.15%), 92Mo(14.53%). Detector : Canberra GC3019 HPGe - efficiency : 30% - energy resolution : 0.9 keV at 122 keV , 1.9 keV at 1.33 MeV Bremsstrahlung photons Converter e- Target of study Electron accelerator Transport to detector Irradiated target HPGe Detector Parameters of 3 experiments Endpoint of Bremsstrahlung photons 67.7 MeV 29.1 MeV 19.5 MeV Duration of irradiation 4h 25m 1h 03m 1h Duration of measurement 138h 39m 196h 39m 18h 34m

Theoretical Calculation n - number of irradiated nuclei of the isotope under study; σ(E) - reaction cross section, which depends on the energy E; Ethr - reaction threshold; Em – endpoint of photon energy; W(E,Em) - bremsstrahlung photon spectrum, its endpoint is E­m; *in this calculation reconstructed by GEANT4; 𝑌 𝐸 𝑚 =𝑛 𝐸 𝑡ℎ𝑟 𝐸 𝑚 𝜎 𝐸 𝑊 𝐸, 𝐸 𝑚 𝑑𝐸 Calculated cross-sections on the basis of combined photonucleon-reaction model Isotope yield of photonuclear reaction on the natural mixture of Mo

T1/2 (decay type of final-state nucleus) Results – 67.7MeV Reaction Final-state nucleus (JP) T1/2 (decay type of final-state nucleus) Threshold (MeV) 67.7MeV Experimental yield (error) Theoretical yield 100Mo(γ,n) 99Mo (1/2+) 67h (β-) 8.29 100 (6) 100 100Mo(γ,pn) 98mNb (5+) 51min (β-) 18.10 0.31 (0.03) 98Mo(γ,p) 97Nb (9/2+) 72min (β-) 9.79 6.6 (0.1) 7.8 97Mo(γ,p) 98Mo(γ,pn) 96Nb (6+) 2.4h (β-) 9.23 17.87 11 (1) 7.7 2.4 10.1 96Mo(γ,p) 97Mo(γ,pn) 95Nb (9/2+) 35d (β-) 9.3 16.72 5.1 (0.4) 10.6 (0.5) 10.0 (γ,p) 15.0 95mNb (1/2-) 3.6d (IT + β-) 9.53 16.95 5.5 (0.3) 5.0 (γ,pn) 94Mo(γ,pn) 92Nb (7+) 92Nb (2+) 3.5 x 107yr (ε) 10.2d (ε) 17.32 17.45 2.60 (0.02) 3.0 92Mo(γ,n) 91Mo (9/2+) 15.5min (ε) 12.68 34 (5) 65.0 92Mo(γ,2n) 90Mo (0+) 5.6h (ε) 22.78 2.7 92Mo(γ,pn) 90Nb (8+) 14.6h (ε) 19.51 14 (5) 3.5 92Mo(γ,p2n) 92Mo(γ,3n)→89Nb 89Nb (9/2+) 2.0h (ε) 29.59 1.9 (0.2) 0.9 92Mo(γ,3n)→89mNb 89mNb (1/2+-) 66min (ε) 29.62 1.8 (0.3) 92Mo(γ,4n) 88Mo (0+) 8min (ε) 46.39 0.04 (0.01) 0.005

Final-state nucleus (JP) Results – 29.1 and 19.5MeV Reaction Final-state nucleus (JP) T1/2 (decay type of final-state nucleus) Eth (MeV) 29.1MeV 19.5MeV Experimental Yield* (error) Theoretical Yield* yield* (error) 100Mo(γ,n) 99Mo (1/2+) 67h (β-) 8.29 100 (6) 100 100 (5) 98Mo(γ,p) 97Nb (9/2+) 72min (β-) 9.79 2.8 (0.1) 4.9 0.33 (0.05) 0.60 97Mo(γ,p) 98Mo(γ,pn) 96Nb (6+) 2.4h (β-) 9.23 17.87 4.0 (0.3) 5.2 0.7 5.9 0.65 (0.06) 1.1 96Mo(γ,p) 97Mo(γ,pn) 95Nb (9/2+) 35d (β-) 9.3 16.72 4.2 (0.1) 6.8 (γ,p) 9.1 0.69 (0.03) 95mNb (1/2-) 3.6d (IT + β-) 9.53 16.95 2.3 (γ,pn) 92Mo(γ,n) 91Mo (9/2+) 15.5min (ε) 12.68 49.0 (4.0) 65 92Mo(γ,2n) 90Mo (0+) 5.6h (ε) 22.78 0.52(0.03) 0.43 92Mo(γ,pn) 90Nb (8+) 14.6h (ε) 19.51 0.76 (0.35) 0.63 *Both experimental and theoretical yield were normalized to the yield of reaction 100Mo(γ,n)99Mo, which was set to 100

Analysis of the results 2d3/2 2d3/2 1g7/2 1g7/2 2d5/2 2d5/2 N=50 93Mo 1g9/2 1g9/2 2p1/2 2p1/2 1f5/2 1f5/2 2p3/2 2p3/2 1f7/2 1f7/2 n p 92Mo Nucleon separation Energy Shell diagram of molybdenum isotopes As mass number A decreases, Bn increases → En decreases → probability of penetration decreases → Yn decreases → Yn decreases Large difference of Bn between 93Mo and 92Mo → Discrepancy between experimental and theoretical calculation of the yield

Summary Photonuclear reaction experiments were conducted with Bremsstrahlung photon with three different endpoints: 19.5, 29.1 and 67.7 MeV. The theoretical calculations were performed on the basis of combined photonucleon-reaction model. The comparison of two result shows that the theoretical model satisfactory describes the yield of photonuclear reaction. Steep decrease of Bn for 92Mo results in discrepancy between experimental and theoretical calculations. This effect can be interpreted on the basis of the shell structure of molybdenum isotopes.

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