A. M. Hurst

0(gs)+ -->2(1)+ transition strengths in 106Sn and 108Sn.

The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.

First results on in-beam γ spectroscopy of neutron-rich Na and Mg isotopes at REX-ISOLDE

After the successful commissioning of the radioactive beam experiment at ISOLDE (REX-ISOLDE) — an accelerator for exotic nuclei produced by ISOLDE — first physics experiments using these beams were performed. Initial experiments focused on the region of deformation in the vicinity of the neutron-rich Na and Mg isotopes. Preliminary results show the high potential and physics opportunities offered by the exotic isotope accelerator REX in conjunction with the modern Germanium γ spectrometer MINIBALL.

Coulomb excitation of neutron-rich Cd isotopes at REX-ISOLDE

We report on the “safe” Coulomb excitation of neutron‐rich Cd isotopes in the vicinity of the doubly magic nucleus 132Sn. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX‐ISOLDE facility. The γ‐decay of excited states has been detected by the MINIBALL array. Preliminary results for the B(E2) values of 122,124Cd are consistent with expectations from phenomenological systematics.

0{sub gs}{sup +}{yields}2{sub 1}{sup +} Transition Strengths in {sup 106}Sn and {sup 108}Sn

The reduced transition probabilities, B(E2;0{sub gs}{sup +}{yields}2{sub 1}{sup +}), have been measured in the radioactive isotopes {sup 108,106}Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation {gamma} rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0{sub gs}{sup +}{yields}2{sub 1}{sup +})=0.222(19)e{sup 2}b{sup 2} for {sup 108}Sn and B(E2;0{sub gs}{sup +}{yields}2{sub 1}{sup +})=0.195(39)e{sup 2}b{sup 2} for {sup 106}Sn were determined relative to a stable {sup 58}Ni target. The resulting B(E2) values are {approx}30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.

0(gs)(+)-> 2(1)(+) transition strengths in (106)Sn and (108)Sn

The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.

0(gs)(+)-> 2(1)(+) transition strengths in Sn-106 and Sn-108

The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.

0gs+→21+Transition Strengths inSn106andSn108

The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.

Sub-Barrier Coulomb Excitation of {sup 110}Sn and Its Implications for the {sup 100}Sn Shell Closure

The first excited 2+ state of the unstable isotope 110Sn has been studied in safe Coulomb excitation at 2.82 MeV/u using the MINIBALL array at the REX-ISOLDE post accelerator at CERN. This is the first measurement of the reduced transition probability of this state using this method for a neutron deficient Sn isotope. The strength of the approach lies in the excellent peak-to-background ratio that is achieved. The extracted reduced transition probability, B(E2:0+-->2+)=0.220±0.022e2b2, strengthens the observation of the evolution of the B(E2) values of neutron deficient Sn isotopes that was observed recently in intermediate-energy Coulomb excitation of 108Sn. It implies that the trend of these reduced transition probabilities in the even-even Sn isotopes is not symmetric with respect to the midshell mass number A=116 as 100Sn is approached.