| 41. |
- Bergmann, U. C., et al.
(författare)
-
On the beta-decay of C-9
- 2001
-
Ingår i: Nuclear Physics A. - 0375-9474. ; 692:3-4, s. 427-450
-
Tidskriftsartikel (refereegranskat)abstract
- In beta -decay experiments on C-9 at CERN/ISOLDE the beta -strength was determined to the ground state, the 12.2 MeV excited state and the Isobaric Analog State (IAS) at 14.655 MeV in B-9. A large beta -strength asymmetry is deduced for the mirror transitions of C-9 and Li-9 to states around 12 MeV excitation energy. A satisfactory description of the three-body decay from a narrow energy region around the 12.2 MeV resonance is obtained within a sequential model involving the ground and first-excited states of Li-5 and Be-8. From the study of angular correlations the spin of the 12.2 MeV state is determined as 5/2(-). For the first time the population of the IAS is observed in beta -decay and new information on the decay of this state is obtained. The advantages of a closely packed. highly segmented detector setup are demonstrated. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 42. |
|
|
| 43. |
- Bjornstad, T., et al.
(författare)
-
Study of the Giant Gamow-Teller Resonance in Nuclear Beta-Decay - the Case of Ar-32
- 1985
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 443:2, s. 283-301
-
Tidskriftsartikel (refereegranskat)abstract
- Delayed proton and gamma emissions following the β-decay of 32Ar have been studied. The half-life of 32Ar is 98 ± 2 ms, and the T = 2 analogue state in 32Cl lies at the excitation energy 5036 ± 12 keV. From the intensity of the feeding to this state the proton intensities can be converted to an absolute scale leading to a total proton branching ratio of (43 ± 3)%. From proton-gamma coincidence measurements it emerges that (1.9 ± 0.2)% of the protons lead to the first-excited state in 31S. A level scheme up to 8.75 MeV excitation in 32Cl has been constructed and the Gamow-Teller strength function has been deduced. The result is a renormalization of the axial-vector strength to (49 ± 5)% of the free-nucleon value.
|
|
| 44. |
- Bjornstad, T., et al.
(författare)
-
The Doubly Closed Shell Nucleus Sn-132(50)82
- 1986
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 453:3, s. 463-485
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of excited states in 132Sn, fed in the β-decay of 132In, has been investigated. Absolute intensities were deduced from γ-singles measurements. From multi-spectrum analysis of γ-lines the half-life of 132In was determined to be 186 ± 22 ms. A level scheme based on γγ and βγ coincidences is presented. The conversion electron spectrum has been studied and internal conversion coefficients deduced for two low-energy transitions. The total decay energy of 132In was determined, from γ-gated β-spectra, to be Qβ = 13.6 ± 0.4 MeV. A lower limit of 6.968 MeV for the neutron separation energy in 132Sn was deduced from the β-delayed neutron spectrum. The experimental results on the level structure of the doubly closed shell nucleus 132Sn show that the shell model is applicable even far from the valley of stability.
|
|
| 45. |
- Borge, M. J. G., et al.
(författare)
-
Asymmetry in the super-allowed beta-transitions of the A=9 isobars
- 2004
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 738:1-4 SUPPL., s. 206-210
-
Tidskriftsartikel (refereegranskat)abstract
- We report here on the recent beta-decay studies of the A = 9 isobar made at ISOLDE/CERN. Mirror beta transitions in the A=9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in Be-9 (11.8 MeV) and B-9 (12.2 MeV) fed in the beta-decay of Li-9 and C-9 respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. Only differences in the partial decay branches of the breakup channels have been found. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states.
|
|
| 46. |
- Borge, M. J. G., et al.
(författare)
-
Beta-Decay to the Proton Halo State in F-17
- 1993
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 317:1-2, s. 25-30
-
Tidskriftsartikel (refereegranskat)abstract
- In the first experiment at the newly constructed ISOLDE Facility the first-forbidden beta-decay of Ne-17 into the first excited state of F-17 has been measured. It is a factor two faster than the corresponding mirror decay and thus gives one of the largest recorded asymmetries for beta decays feeding bound final states. Shell-model calculations can only reproduce the asymmetry if the halo structure of the F-17 state is taken into account.
|
|
| 47. |
- Borge, M. J. G., et al.
(författare)
-
Beta-delayed multiparticle emission studies at ISOL-type facilities
- 2004
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 746, s. 243-243
-
Konferensbidrag (refereegranskat)abstract
- We report here on the recent beta-decay studies made at ISOL-type Facilities to determine the multiparticle breakup mechanism of excited states in light nuclei by studying them in full kinematics. In particular the results obtained for the A = 9 isobars and the breakup of the 12.7 MeV state in C-12 of unnatural parity are discussed. The breakup of the latter has been debated since more than a decade. Mirror beta transitions in the A = 9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in Be-9 (11.8 MeV) and B-9 (12.2 MeV) fed in the beta-decay of Li-9 and C-9 respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. The controversy on the breakup mechanism of the 12.7 MeV state is resolved.
|
|
| 48. |
- Borge, M. J. G., et al.
(författare)
-
Beta-Delayed Proton and Alpha Emission in the Decay of Ne-17
- 1988
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 490:2, s. 287-306
-
Tidskriftsartikel (refereegranskat)abstract
- The beta-delayed proton and alpha spectra from 17Ne have been studied with Si-detectors. The Gamow-Teller strength in the decay of 17Ne has been extracted and compared with a two-particle-one-hole shell-model calculation. The experimental strength is quenched by a factor of 0.82 with respect to the calculated one. Furthermore, the decay scheme has been improved and is discussed in some detail. The proton emitting levels in 17F are very broad and the line shapes are strongly influenced by phase-space effects. Interference between peaks corresponding to the same intermediate spin is a prominent feature emerging clearly with the good resolution and statistics of the present work.
|
|
| 49. |
- Borge, M. J. G., et al.
(författare)
-
Beta-Delayed Triton Emission in the Decay of He-8
- 1986
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 460:3, s. 373-380
-
Tidskriftsartikel (refereegranskat)abstract
- A β-delayed triton branch with an intensity of (0.9 ± 0.1)% has been observed in the decay of 8He. The triton energy spectrum was measured with a specially designed ΔE − E telescope. These data as well as an earlier measured β-delayed neutron spectrum cannot be explained from the known levels in 8Li, but it turns out that the main features of both the delayed triton and the delayed neutron spectra from 8He could be understood if one assumes a new state in 8Li at about 8.8 MeV excitation energy.
|
|
| 50. |
- Borge, M. J. G., et al.
(författare)
-
Elucidating halo structure by beta decay: beta gamma from the Li-11 decay
- 1997
-
Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 55:1, s. R8-R11
-
Tidskriftsartikel (refereegranskat)abstract
- New values for the gamma ray intensities following the beta decay of Li-11 are presented. Special emphasis is put on the determination of the Gamow-Teller transition Li-11 --> Be-11 (1/2(-), 320 keV) to the only bound excited state in Be-11. We show that a shell-model calculation can simultaneously reproduce the half-life of Li-11 and the newly measured branching ratio to the 1/2(-) state provided the Li-11 ground state wave function contains about 50% of s-wave neutron components.
|
|
