J. Mierzejewski

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.

SUPPORT FOR THE CHIRAL INTERPRETATION OF PARTNER BANDS IN 128Cs – THE ELECTROMAGNETIC PROPERTIES

Results of the DSAM lifetime measurements in supposed chiral partner bands of 128Cs and 132La are presented. Experimental reduced transition probabilities in 128Cs are compared with theoretical calculations done in the frame of the Core-QuasiParticle Coupling model. The electromagnetic properties and energy pattern of partner bands show that 128Cs is the best candidate revealing the chiral symmetry breaking phenomenon.

Spontaneous time-reversal symmetry breaking in 124Cs

Preliminary results of DSA lifetime measurements in the partner bands of 124Cs are presented. The 124Cs nucleus was produced in the 114Cd(14N,4n)124Cs reaction at the Heavy Ion Laboratory of the University of Warsaw. A phenomenon of spontaneous time-reversal symmetry breaking in 124Cs nucleus is discussed. Appearance of a critical rotational frequency being the point of phase transition to time-reversal symmetry breaking configurations is suggested.

DSA lifetime measurements of 124Cs and the time-reversal symmetry

A hypothesis of the chiral symmetry breaking opened a new opportunity for the study of spontaneous time-reversal symmetry breaking in an atomic nucleus. The occurence of chirality has been found in 126,128Cs nuclei for which specific electromagnetic selection rules have been found in Doppler Shift Attenuation experiments. Here, recent DSA measurements in the 124Cs nucleus are presented. The 124Cs nucleus was produced in the 114Cd(14N,4n)124Cs reaction at Heavy Ion Laboratory of the University of Warsaw. The obtained results agree with basic expectations deduced from the chiral symmetry breaking. A connection between the chirality phenomenon and the time-reversal symmetry is discussed and a possibility of using chiral doublets for studies of fundamental time reversal symmetry is suggested.

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.