0. 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 : /S X
2015 KPS fall Meeting
Han Dong Yoon
Skobeltsyn Institute of Nuclear Physics
Faculty of Physics MSU

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

2. 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 s p n γ
90Mo
ε /β+
T1/2 = 5.56 h s
90Nb
92Mo

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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.

9. Thank you for attention!