The Gamow-Teller beta decay of neutron-deficient even isotopes of tin

Abstract

With the use of the 58Ni+S~ fusion-evaporation reaction and chemically selective on-line mass separation, the EC//3 + decay of t~ was studied by ?-ray and conversionelectron spectroscopy. In the course of these studies, a new 15.7-s isomeric state of t~ was observed. Reinvestigation of the {/-decays of the two heavier even isotopes of tin, produced in the s 8Ni + 58Ni reaction and mass separated without chemical discrimination, brought new information on the decay of l~ and ~~ The QEc values of 1~ l~ and 1~ were determined to be 4550 +300 keV, 3200+100 keV and -250 <2270 keV, respectively. In the data analysis, the emphasis is put on the identification of the 0+-~ 1 + Gamow-Teller /~ transitions and determination of their strengths. For 1~176 the total Gamow-Teller strengths are measured to be 20% to 30% of that predicted by the single-particle shell model with the inclusion of pairing correlations and core polarization. Predictions of the decay properties of the as yet unobserved ~~ and l~176 are made. 23.40.Hc; 21.10.Dr; 21.10.Pc; 27.60. +j; 29.30.Kv PACS: IntroductionThis paper presents a reinvestigation of the 104, 106,1088n EC/fl+ decays carried out at the GSI mass separator on-line to the UNILAC with the application of nuclear spectroscopy techniques. In the data analysis, the emphasis is put on the identification of the 0+~ 1 + Gamow-Teller (GT) transitions and determination of their strengths. The observation of more than one GT transition in each of the three decays, and the origin of quenching of the summed GT strengths compared to prediction of the extremesingle-particle shell model (ESPSM) are discussed with reference to theoretical studies [1][2][3].The main new results are those obtained for A = 104. Compared to our preceding investigation of the isotope ~~ [4,5] (see also the Leuven results * This work is part of the Ph.D. thesis of G.-E. Rathke[6]), an essential progress in studying its decay properties has been achieved due to the application of a mass-separator ion source [7,8] which allows for a substantial suppression of the isobaric contamination. Also the application of a mini-orange spectrometer [-9] for measuring the spectra of internal-conversion electrons appeared to be a very important addition to our 7-ray studies. As a result, the l~ --+ 1~ decay scheme is constructed with four wellestablished GT transitions.Four GT transitions (two of which were not reported in [10,11]) have also been observed in the 1~ decay. The previous version of the 1~ decay scheme [12, 13] has essentially been confirmed with respect to GT strength. Finally, the results of the present work have been extrapolated to get an estimate of the decay properties for the yet unobserved isotopes 1~and doubly magic l~176

Gamow-Teller strength in the ?+ decay of104In

“…In Fig. 5, this decay pattern is compared with the decay of an even-even nucleus (l~ 1,20] and of an odd nucleus (t~ 1,26]. A simplified explanation for the similarities is that small logft values are associated with the core decay (0 +--.1+), while large logft values are associated with the decay of the unpaired proton.…”

“…The total GT strengths of neutron-deficient even isotopes of tin, for instance, are measured to be ~10% of those predicted by the Extreme Single-Particle Shell Model [20]. Even with the inclusion of pairing correlations and core polarization, the quenching remains considerable (10-30%) [20]. Further theoretical work on this matter can be found in [19] and [21] to [24] (and the references therein).…”

“…However, the Gamow-Teller strength determined from /3+/EC decay is also significantly quenched compared to simple shell-model estimates based on one-body operators and free-nucleon coupling constants [19]. The total GT strengths of neutron-deficient even isotopes of tin, for instance, are measured to be ~10% of those predicted by the Extreme Single-Particle Shell Model [20]. Even with the inclusion of pairing correlations and core polarization, the quenching remains considerable (10-30%) [20].…”

Three decades of research using IGISOL technique at the University of Jyväskylä

“…Lastly, the reaction rate has also been calculated using theoretical three-body calculations which in recent years have been performed by several groups [95][96][97][98][99]. These have been followed up by evaluations of the potential effect of the rate changes on neutron stars [100], white dwarfs [101], and low-mass stars [102].…”

Nuclear Decay Studies Far from Stability

“…'J 1 for the N=82 region and by Barden et a/. 32 for the Z=50 region (1t~1 2~v~12 transitions). Towner 33 has argued that these discrepancies are due to pairing correlations, core polarization, and higher-order phenomena.…”