neutron-particle 210 Bi nucleus Natalia Cieplicka- Oryczak INFN, - PowerPoint PPT Presentation

High- and low-spin structures in the proton-particle neutron-particle 210 Bi nucleus Natalia Cieplicka- Oryńczak INFN, Sezione di Milano, Milano, Italy Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland

Outline Why the 210 Bi nucleus?  An ideal nucleus for testing the shell- model calculations : couplings between valence proton and valence neutron Z=82  An ideal system for studying phonon (3 – of 208 Pb)-valence particles coupling N=126 Experimental data 210 Bi  Low-spin structure – neutron capture 208 Pb experiment at Institute Laue-Langevin (Grenoble, France)  High-lying yrast states – deep-inelastic reactions for the system 208 Pb + 208 Pb (Argonne National Laboratory, USA)

Experiment – ILL Grenoble (PF1B line) 8 EXOGAM clovers 6 GASP detectors γ 2 ILL clovers n 210 Bi 209 Bi γ γ Cold neutron flux of 209 Bi solid Population of capture state in 2  10 10 /(ns  cm 2 ) from 210 Bi at binding energy of target (3g) the ILL reactor with 4.6 MeV energy < 5 meV 16 Ge detectors of EXILL array: 8 of EXOGAM, 6 of GASP, and 2 from ILL collaboration – coincidence measurements of gamma rays

Experiment – ILL Grenoble (PF1B line) 8 EXOGAM clovers 6 GASP detectors 2 ILL clovers 16 Ge detectors of EXILL array: 8 of EXOGAM, 6 of 8 detectors of EXOGAM arranged into ring around the target at GASP, and 2 from ILL collaboration – coincidence every 45° so angular correlation measurements could be measurements of gamma rays performed

Experimental results: level scheme γ γ n 210 Bi 209 Bi γ γ (4 – , 5 – ) 9/2 – 0 4.6 MeV Capture state 209 Bi at neutron binding energy 1 – 0

4605 320 0 210 Bi

320 674 1013 4605 2599 1013 674 320 0 210 Bi

611 944 645 311 4605 2023 1055 611 944 645 311 271 0 210 Bi

Experimental results: level scheme 64 primary transitions Population of neutron capture state at 4605.2(1) keV (40 new) 4605 70 excited states (33 new) 0 210 Bi

Angular correlations of g rays from 210 Bi The angular correlation function for a pair of coincident g 3+ 993 rays connecting the nuclear states with spins J i  J  J f is g 1 usually expressed as: 674  2- W( Θ ) = 1 + A 2 P 2 (cos Θ ) + A 4 P 4 (cos Θ ) 320 320 g 2 1- 0 Θ – the angle between the direction of emission of two g rays P n (cos Θ ) – Legendre polynomials A n = q n A (1) A (2) – the coefficients which depend on the attenuation factor q n as well as on the multipolarities of 1 and 2 674 keV g rays and the spins of involved nuclear states 0 degree 45 degree q 2 = 0.86(2) 90 degree q 4 = 0.60(3) Counts Normalization: number of pairs of the detectors, efficiency  W( Θ ) norm0 = 0.495(5) (4 combinations) norm45 = 2.020(12) (16 combinations) norm90 = 1 (8 combinations) Energy [keV]

4-, 5- 4605 Spin-parity assignments  J=1(+2)  J=0(+1)  J=0(+1)  J=0(+1)  J=1(+2)  J=0(+1) W W W 1.4 1.4 W 2505-393 1.4 2505-320 1.4 2505-674 2505-1596 1.3 1.3 1.3 1.3 1.2 1.2 1.2 1.2 1.1 1.1 1.1 1.1 1. 1. 1. 1. 0 0 0.9 4 2 0.9 0 4 2 0 0.9 0.9 4 2 4 2 0.8 A 2 =-0.14(2), A 4 =-0.03(3) 0.8 A 2 =-0.13(2), A 4 =-0.02(5) A 2 =0.24(3), A 4 =-0.01(6) 0.8 0.8 A 2 =-0.11(2), A 4 =0.03(4) 0.7 0.7 0.7 0.7 δ 2505 =0.04(8) δ 393 =-0.3(3) δ 2505 =0.07(12) δ 1596 =0.01(3) ( δ 2505 =-0.82(12)) ( δ 2505 =-0.88(19)) E2 E2 E2 M1+E2 E2 M1(+E2) W W W 1.3 1.3 2624-1709 1.3 2624-1430 2624-1398 (5) 2100 1.2 1.2 1.2 1.1 1.1 1.1 1. 1. 1. 1981 7 – 0 0 0 0.9 0.9 4 2 0.9 4 2 4 2 A 2 =0.11(3), A 4 =0.04(5) A 2 =-0.10(3), A 4 =0.02(7) 0.8 0.8 0.8 A 2 =-0.19(3), A 4 =0.00(7) 0.7 0.7 0.7 4 + δ 1398 =0.05(5) δ 1430 =-0.11(5) 1524 M1(+E2) M1(+E2) (E1) W W W 530-674 1.2 1.2 530-320 1175-320 1.2 1.1 1.1 1.1 1. 1. 1. 0 0 4 2 0 4 2 0.9 4 2 0.9 0.9 A 2 =0.01(1), A 4 =-0.03(3) A 2 =0.04(3), A 4 =0.03(6) A 2 =0.02(1), A 4 =-0.02(2) 0.8 0.8 0.8 δ 530 =0.09(3) δ 530 =0.06(2) δ 1175 =0.03(5) 0 1-

4-, 5- 4605 Spin-parity assignments  J=1(+2)  J=1(+2)  J=1(+2) W W W 1013-674 1.3 1013-320 1659-320 1.3 1.3 1.2 1.2 1.2 1.1 1.1 1.1 1. 1. 1. 0 0 0 0.9 4 2 0.9 4 2 0.9 4 2 A 2 =0.10(5), A 4 =-0.01(11) 0.8 A 2 =0.10(2), A 4 =0.01(4) 0.8 0.8 A 2 =-0.06(5), A 4 =-0.08(10) 0.7 0.7 0.7 δ 1013 =-0.10(4) δ 1659 =0.23(14) δ 1013 =-0.11(9) (E2) M1(+E2)  J=1 M1(+E2) M1(+E2) (M1) W W W 3633-563 (5) 2100 1.2 1.2 1.2 634-563 409-563 (4) 2007 1.1 1.1 1.1 1981 7 – 1. 1. 1. 0 0 0 (7-) 4 2 4 2 4 2 0.9 0.9 0.9 A 2 =0.10(3), A 4 =0.03(6) 1527 A 2 =-0.05(4), A 4 =-0.02(8) A 2 =-0.07(6), A 4 =-0.05(11) 4 + 0.8 0.8 1524 0.8 δ 563 =0.10(8) δ 563 =0.25(30) (2) 1197 (M1) (M1) W 1.3 611-645 1.2 1.1 1. 0 4 2 0.9 A 2 =0.07(5), A 4 =0.07(11) 0.8 0 1-

Comparison with shell-model calculations for low-spin states Kuo-Herling interactions were used. Firmly known states used to fit TBME of p-n interaction E. K. Warburton, B. A. Brown, Phys. Rev. C 43, 602 (1991) Observed in other experiments Shell-model calculations Experimental results (EXILL) 210Bi

Comparison with shell-model calculations for low-spin states 3120 (2,3,4) 3097 3 – × ( π h 9/2 ν g 9/2 ) 3045 3023 (3,4) 2979 3- × 0-  3+ 3- × 1-  2+, 3+, 4+ (4,5,6) 2883 3- × 9-  6+, 7+, 8+, (9+, 10+, 11+, 12+) (3,4,5) 2807 (4,5,6) 2730 (3,4,5) 2726 3 – 2.6 MeV 2556 (4,5) (5) 2147 4(+) 2007 Experimental Shell-model 0+ 0 Observed in results (EXILL) calculations other experiments 210Bi 208Pb

Deep-inelastic collisions γ γ γ beam 208 Pb beam on 208 Pb target (76mg/cm 2 )   Energy: 1446 MeV (7 MeV/nucleon) beam target  Pulsed beam prompt and delayed gamma-gamma coincidences  Detectors of Gammasphere divided into 6 rings around beam axis with average values of  angle: 17.3°, 35.5°, 52.8°, 69.8°, 79.9°, 90.0° Gammasphere, Argonne National Laboratory, USA

210 Bi – level scheme Previously known part of the level scheme (B. Fornal, Habilitation thesis, Raport No. 1939/PL (2004)) Counts Previously known Observed in present studies Counts E g [keV] The sum of delayed spectra (double gates on every pair of previously known transitions: 398, 653, 1403, 1514 keV)

210 Bi – level scheme Evidence of high-lying isomer at ~10 MeV excitation 211, 217, 350, 358, 362, 371, 414, 439, 783, 1104 keV Counts Previously known Observed in present studies Counts E g [keV] The sum of delayed spectra (double gates on every pair of previously known transitions: 398, 653, 1403, 1514 keV)

Angular distributions of g rays from 210 Bi The angular distribution function for a transition J i  J f , Spin alignment where J represents the spin of nuclear state, is usually J 1 expressed as: l i W( Θ ) = 1 + A 2 P 2 (cos Θ ) + A 4 P 4 (cos Θ ) l f g J 2  beam Entrance angular Angular momentum Exit relative angular momentum momentum l i transfer from orbital l f and intrinsic spins J 1 , J 2 of the Θ – the angle between the beam direction and the direction of g ray into intrinsic spin fragments emission P n (cos Θ ) – Legendre polynomials max – the coefficients which depend on the attenuation A n = α n A n Angular momentum is divided between the fragments factor α n as well as on the multipolarity of a according to their masses (assuming rigid rotation) g ray and the spins of involved nuclear states α 2 = 0.6(1) 5   α 4 = 0.2(5) J A 3    1 1     J A Normalization: isotropic distribution of the 516-881-803-keV cascade 2 2 deexciting the 125- μ s isomer in 206Pb.

Angular distributions of g rays from 210 Bi E1 653 keV E3 224 keV 1403 keV M1+E2 398 keV 151 keV M1+E2 783 keV M1/E1 M1+E2 371 keV 1050 keV 1252 keV E2 M2(+E3) M2(+E3) E1 744 keV 1821 keV M1+E2 Con onversio ion coeffic icie ients α E [keV] Type 131 4.78(48) M1 2613 keV 1514 keV 151 3.17(28) M1(+E2) 154 5(2) M1 M2(+E3) M1+E2 175 0.7(1) E2 224 0.98(9) M1(+E2) 398 0.19(5) M1(+E2)

210 Bi – spin-parity assignments for the yrast states (20 – ) E1 653 keV E3 224 keV 1403 keV M1+E2 (19 – ) (17 – ) 398 keV 151 keV M1+E2 783 keV M1/E1 M1+E2 (16 – ) (15 – ) (14 – ) (16 + ) 371 keV 1050 keV 1252 keV (15 + ) E2 (13 + ) M2(+E3) M2(+E3) E1 744 keV 1821 keV M1+E2 Con onversio ion coeffic icie ients α E [keV] Type 131 4.78(48) M1 2613 keV 1514 keV 151 3.17(28) M1(+E2) 154 5(2) M1 M2(+E3) M1+E2 175 0.7(1) E2 224 0.98(9) M1(+E2) 398 0.19(5) M1(+E2)

210 Bi – shell-model calculations for the yrast states Couplings with 3 – excitation The higher states involve the promotions of at 2615 keV in 208 Pb proton or neutron across the energy gap – the calculations with the core excitations must be performed ( π h 9/2 ν j 15/2 )12 + × 3 – ( π i 13/2 ν g 9/2 )11 + × 3 – ( π h 9/2 ν g 9/2 )10 – × 3 – 210 Bi structure arises from 1-p 1-n couplings up to the 2725-keV state (14 – ) 3p 1/2 3p 3/2 2f 5/2 3d 3/2 2g 7/2 4s 1/2 1i 13/2 3d 5/2 1j 15/2 Firmly known states 2f 7/2 1i 11/2 used to fit TBME of p-n interaction 1h 9/2 2g 9/2 E. K. Warburton, B. A. Brown, Phys. Rev. 208 Pb C 43, 602 (1991) neutrons protons

Spin distribution (experimental results) 10 16 12 9 14 – from π i 13/2 ν j 15/2 Full multiplet π h 9/2 ν g 9/2 Newly found states