S. H. Liu, 1 J. H. Hamilton, 1 A. V. Ramayya, 1 A. Covello, 2 A. Gargano, 2 N. Itaco, 2 Y. X. Luo, 1,3 J. O. Rasmussen, 3 S. J. Zhu, 4 J. K. Hwang, 1 A.V.Daniel, 1,5 G.M.Ter-Akopian, 5 Y. Oganessian 5, N. J. Stone, 6,7 J. R. Stone 7 1. Vanderbilt University 2. University of Napoli, Complesso Universitario di Monte San Angelo 3. Lawrence Berkley National Lab 4. Tsinghua University 5. Joint Institute for Nuclear Reaction 6. University of Tennessee 7. Oxford University
EXPERIMENTAL METHODS Lawrence Berkeley National Laboratory. Gammasphere Detector Array with 101 Comptonsuppressed Ge Detectors. 252 Cf Source of 62 µci, stopped in iron foils. Total of 5.7x10 11 triple and higher fold γ γ γ coincidence events (in cube). Triple coincidence data were sorted into 64 two dimensional histograms corresponding to the 64 angle bins for the angular correlation studies.
134 I 133 I 137 136 80 I 135 I 84 83 I 82
134 I
134 I ν(h11/2) π(g7/2) 3 π(g7/2) 2 (2d5/2) 1 See Liu et al, PRC 79, 067303 (2009) and Coraggio et al. PRC 80, 061303(R) (2009) for details in experiment and theory, respectively.
N=84 Isotones: 137 I and 139 Cs 137 I : 3 new levels with 4 new transitions. 139 Cs: 10 new levels with 18 new transitions.
Spin-parity Assignment in 139 Cs J Π = 7/2 + for the ground state [1]. J Π of the excited levels, determined by measuring γ-γ angular correlations and the ICC of the 236.9 kev transition. Cascade (kev) A exp 2, A exp 4 A the 2, A the 4 (Q->Q) 475.3->595.4-0.10(1), -0.01(2) 428.2->475.3 0.11(1), 0.00(2) 0.10, 0.0 740.4->428.2 0.11(2), -0.02(3) 0.10, 0.0 727.9->740.4 0.11(3), -0.01(4) 0.10, 0.0 544.6->601.6 0.09(2), 0.01(3) 0.10, 0.0 589.8->544.4 0.10(4), -0.00(7) 0.10, 0.0 α T (236.9)=0.086(12): M1/E2 mixture. Multipolarities: 595.4 (M1/E2, δ=-4.2 +0.4-0.5 or -0.07(2) ), 475.3(E2), 428.2(E2), 740.4(E2), 727.9(E2), 601.6(E2), 544.4(E2) and 589.8(E2). [1] Table of Isotopes, 8th ed., edited by R. B. Firestone and V. S. Shirley (Wiley: New York, 1996).
Shell-Model Calculations for 137 I and 139 Cs 137 I: 3 valence protons and 2 neutrons beyond 132 Sn. 139 Cs: 5 valence protons and 2 neutrons beyond 132 Sn. 132 Sn as a closed core, valence protons in 0g 7/2, 1d 5/2, 3/2, 1s 1/2, 0h 11/2 and neutrons in 0h 9/2, 1f 7/2, 5/2, 2p 3/2, 1/2, 0i 13/2, the two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential [1], 5 valence-proton and 6 valence-neutron energies taken from the experimental spectra of 133 Sb and 133 Sn except πs 1/2 and νi 13/2 levels [1], OSLO shell model code [2]. [1] L. Coraggio, A. Covello, A. Gargano, and N. Itaco, Phys. Rev. C 72, 057302 (2005). [2] T. Engeland, The Oslo shell-model code, unpublished, 1991-2006.
Shell-Model Calculations for 137 I and 139 Cs Reproduce the level pattern rather well up to 29/2 + in both nuclei. 137 J π E exp E J π E exp E I calc calc 139 Cs 7/2 + 0 0 7/2 + 0 0 5/2 + 244 255 9/2 + 554 684 11/2 + 621 685 13/2 + 955 1065 15/2 + 1109 1154 17/2 + 1313 1305 19/2 + 1609 1474 21/2 + 2038 2168 23/2 + 2224 2501 25/2 + 2744 2949 27/2 + 3086 3177 29/2 + 3168 3242 31/2 + 3653 4181 33/2 + 3854 4353 35/2 + 4410 6582 37/2 + 4189 7069 41/2 + 4947 7175 5/2 + 219 159 9/2 + 595 710 11/2 + 602 688 13/2 + 1071 1141 15/2 + 1146 1192 17/2 + 1499 1426 19/2 + 1736 1607 21/2 + 2239 2338 23/2 + 2492 2691 25/2 + 2967 3100 27/2 + 3338 3406 29/2 + 3496 3472 31/2 + 4145 4464 33/2 + 4324 4593 37/2 + 4670 5824 δ the (595.4)= -3.6, close to -4.2 +0.4-0.5, favoring E2. Large discrepancy at high spin may reflect limits of chosen model space. See Liu et al. PRC 80, 044314 (2009)
Spin-parity Assignments in N=83 isotones: 135 Te, 136 I, 137 Xe, 138 Cs
Spin-parity Assignments in N=83 isotones: 135 Te, 136 I, 137 Xe, 138 Cs The shell-model calculations performed using the OXBASH computer code [1]. [1] B. A. Brown, et al., The computer code OXBASH, MSU-NSCL, Report No. 524.
Spin-parity Assignments in N=83 isotones: 135 Te, 136 I, 137 Xe, 138 Cs
Spin-parity Assignments in N=83 isotones: 135 Te, 136 I, 137 Xe, 138 Cs
g-factor of the 15/2 state in 137 Xe The fission fragments implanted and stopped in the iron foils, subject to the hyperfine fields (B HF ) caused by their implantation in substitutional sites in the iron lattice. It becomes possible for us to carry out angular correlation measurements to determine the g-factors of long-lived states by using the integral perturbed angular correlation (IPAC) technique. The result of the rotation of the implanted nucleus about the B HF is an attenuation of the expected angular correlation coefficients.
g-factor of the 15/2 state in 137 Xe
g-factor of the 15/2 state in 137 Xe E2 E2 E2 G 2 =0.072/0.102=0.71(7), B HF (Xe)=73(8) T [1], Lifetime calc =0.6 ns g =0.26(5) [1] G. N. Rao, Hyperfine Interact. 26, 1119 (1985). Shell-model calculations, g calc =0.31. See Liu et al. PRC 81, 014316 (2010) for more details in shell-model calculations.
Summary Level scheme of 134 I was identified for the first time and reproduced by shell-model calculations. N=84 isotones 137 I and 139 Cs were re-investigated and level patterns were predicted by shell-model calculations up to 29/2 +. Spin-parities of levels in N=83 135 Te, 136 I, 137 Xe, 138 Cs were assigned based on angular correlation measurements, confirmed by shell-model calculations. g-factor of the 15/2 state in 137 Xe was determined, consistent with the calculated value from shellmodel calculations.