High Resolution 148 Nd3 He n Two Proton

High Resolution 148 Nd(3 He, nγ) Two Proton Stripping Reaction and the structure of the 02+ State in 150 Sm J. F. Sharpey-Schafer 1, P. Papka 2, 3, S. P. Bvumbi 4, P. Jones 3, P. Vymers 2, R. A. Bark 3, T. D. Bucher 3, T. S. Dinoko 1, J. L. Easton 1, M. S. Herbert 1, P. V. Keshwa 2, N. Khumalo 1, E. A. Lawrie 3, J. J. Lawrie 3, S. N. T. Majola 3, 5, J. Ndayishimye 2, M. R. Nchodu 3, D. Negi 3, S. P. Noncolela 1, J. N. Orce 1, O. Shirinda 3, P. Sithole 1, M. A. Stankiewicz 5 and M. Wiedeking 3 1 Department of Physics, University of Western Cape, South Africa 2 Department of Physics, Stellenbosch University, South Africa 3 Department of Nuclear Physics, i. Themba LABS, South Africa 4 Department of Physics, University of Johannesburg, South Africa 5 Department of Physics, University of Cape Town, South Africa

i. Themba LABS Near Cape Town AFRODITE = AFRican Omnipurpose. Detector for Innovative. Techniques and Experiments 9 Clover HPGe in BGO Shields 8 LEPS each with 4 quadrants DAIMANT T-o-F Recoil Detector Frozen 136 Xe target Neutron Wall Solar Cell HI detector checkerboard High Energy Capture γ-rays 2 High Resolution (3 He, n) two proton stripping

JFS-S et al. , Eur. Phys. J. A 47 (2011) 5 154 64 Gd 90

Congruence of first & second Vacuum structures in 154 Gd & 152 Sm JFS-S et al. , Eur. Phys. J. A 47 (2011) 5

Configuration Dependent or Quadrupole Pairing; Assume Δpp≈ Δoo>> Δop [660]1/2+ “Prolate” R. E. Griffin, A. D. Jackson and A. B. Volkov, Phys. Lett. 36 B, 281 (1971). W. I. van Rij and S. H. Kahana, Phys. Rev. Lett. 28, 50 (1972). [505]11/2“Oblate” S. K. Abdulvagabova, S. P. Ivanova and N. I. Pyatov, Phys. Lett. 38 B, 251 (1972). 82 Neutrons D. R. Bès, R. A. Broglia and B. Nilsson, Phys. Lett. 40 B, 338 (1972). Prolate Deformation => I. Ragnarsson and R. A. Broglia, Nucl. Phys. A 263, 315 (1976).

JFS-S et al. , Eur. Phys. J. A 47 (2011) 6 Kπ=15/2=2γ+ + [505]11/2 - 155 Gd 91 High-K Decay Scheme Missing │02+ > coupling [505]11/2 -

Suzan P. Bvumbi et al. , Phys. Rev. C 87 (2013) 044333 Partial level schemes of 150 Sm (a) and 152 Gd (b) showing the ground state, second vacuum 02+ and octupole bands. New transitions and E 1 transitions from the second vacuum 02+ bands to the octupole bands are shown in red.

Phys. Rev. C 41, (1990) R 1351 150 62 Sm 88 Z=62 Zang et al. Phys. Rev. C 81 (2010) 034302; Relativistic mean-field Jerzy Dudek & Dominque Curian; private communication

Slide from W. David Kulp

There are only two examples where the double beta 2β 2ν decay to excited states in a nucleus has been measured. These are; 100 Mo → 100 Ru first excited 02+ partial lifetime T 1/2 = 1. 6(~6)x 1020 yr. 150 Nd → 150 Sm first excited 0 + 2 partial lifetime T 1/2 = 1. 33(~30)x 1020 yr. Frank T. Avignone III, Steven R. Elliott and Jonathan Engle, Rev. Mod. Phys. 80, 481 (2008).

θ = 6° Two Neutron Pick-up 152 Sm(p, t)150 Sm A. Saha et al. , Phys. Lett. 85 B, 215 (1079). θ = 27° Two Neutron Stripping 148 Sm(t, p)150 Sm J. H. Bjerregaard et al. , Nucl. Phys. 86, 145 (1966).

Two Proton Stripping Reactions 3 He, n) Sn Cd( 48 50 ΔE ≈ 500 ke. V Time-of-Flight → Neutron detector 9 m 3 He Target beam 25. 4 Me. V H. W. Fielding et al. , Nucl. Phys. A 281, 389 (1977 ) {W P Alford and friends}

THE PROBLEM for (3 He, n) Two Proton Stripping: 1. How to get good resolution ΔEn ≈ 2 ke. V 2. How to separate the 1 in 1000 (3 He, n) direct reaction events from the flood of (3 He, xn) fusion-evaporation events ? ? THE SOLUTION: 1. Use HPGe detectors having ΔEγ ≈ 2 ke. V 2. (i) Note that Q (3 He, n) ≈ + 7 Me. V En ≈ 32 Me. V Fast while Q (3 He, xn) ≈ - 17 Me. V En < 6 Me. V Slow (ii) To 0+ states, the (3 He, n) cross-section peaks at 0° while for (3 He, xn) all neutrons are emitted isotropically ie. the direct reaction L=0 neutrons to 0 n+ states are focused at 0° While the evaporation neutrons are emitted in all directions.

AFRODITE = AFRican Omnipurpose Detector for Innovative Technologies and Experiments target 12 Neutron detectors Each 10 x 60 cm beam stop AFRODITE 9 HPGe Clovers in BGO shields 25 Me. V 3 He beam Pb γ-ray shielding wall ~2. 0 m Schematic set-up for (3 He, n) experiments

We have measured: 148 Nd(3 He, n)150 Sm and 98 Mo(3 He, n)100 Ru at 25 Me. V (a) 148 Nd(3 He, n)150 Sm Q-values and fusion-evaporation Cross-sections 1 n => + 6. 512 Me. V 150 Sm <0. 1% 2 n => - 1. 474 Me. V 3 n => - 7. 348 Me. V 148 Sm 64% 464 mb (3 n) 4 n => -15. 488 Me. V 147 Sm 34% 249 mb (4 n) (b) 98 Mo(3 He, n)100 Ru Q-values Cross-sections 1 n => + 7. 971 Me. V 100 Ru <0. 1% 2 n => - 1. 702 Me. V 99 Ru 5. 8% 51 mb (2 n) 3 n => - 9. 171 Me. V 98 Ru 81. 5% 716 mb (3 n) 4 n => -19. 420 Me. V

59 Co (3 He, n)61 Cu 27 32 29 32 Fast Neutrons from (3 He, n) γ-rays from target γ-rays from beam stop Statistical Neutrons from (3 He, xn) P. Papka et al. , submitted to Phys. Rev. C

Initial analysis of 148 Nd(3 He, n)150 Sm 21+ 41+ 61+ from Paul Papka

W. P. Alford et al. , Nucl. Phys. A 321 (1979) 45. All Experiments have snags and/or Flaws !!!! Our Major Snag is that we do NOT DETECT THE GROUND STATE [no γ-rays !!] BUT we are rescued by W P Alford, and his mates, by their low resolution measurements !!!! They can see the ground state and little else. We can then fit their spectra, as an upper limit, as we know the relative strengths of the population of the excited states. Angular Range of our Neutron Detectors θ = 0° to 10°

~5 channels = 1 ns = 550 ke. V Coulex of Target by incoming beam ~7 channels is wider Alford et al. NP A 321 (1979) 45 61+ 140 120 150 Sm Number of Counts 100 152 Sm 1279 03+ 88 1082 152 Sm 90 80 41+ 773 60 02+ 740 02+ 685 21+ 334 41+ 366 21+ 122 61+ 707 40 20 0 1 3 5 7 9 11 13 Channel number 15 17 19 21 01+ 0

140 WPA etal. T-o-F data NP A 321(1979)45 Nd(3 He, n)Sm 120 100 152 Sm normalised to 150 Sm 80 60 150 Sm 40 20 0 1 140 5 7 9 80 13 15 (ke. V) EE (ke. V) gndxx state peak 50 0 40 2+ peak 0 30 4+ peak 0+ 2+ 20 20 40 + 1 3 5 7 9 11 13 15 Channel number 17 19 21 1 6+ γ-rays Fit To. F Fit -- 271(19) 469(25) 334 100(5) 100 1728(77) 173(20) 439 34(4) 585(56) 6+ & 02+ peaks 10 0 21 Total Fit; Four peaks Level 60 40 19 T-o-F data 152 Sm 70 60 17 Relative Counts Intensities 150 Sm in Peaks 150 Sm 80 Counts 100 11 90 T-o-F data 150 Sm Total Fit; Three peaks gnd state peak 2+ peak 4+ peak & 02+ peak 120 Counts 3 3 5 7 9 11 13 15 Channel 218(38) number 506 13(2) 506 22(6) 38(10) 17 19 -- 21

AFRODITE Crew UWC Graduate School Paul Papka R&R