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The processes mediated by the weak interaction have significant implications in nuclear physics, astrophysics, and particle physics. In particular, the electron capture (EC) plays a prominent role in driving the dynamics of core-collapse supernovae, while the β-decay determines the time scale of the nuclear r-process. Both processes are influenced by the underlying nuclear structure through the spin-isospin excitations and the associated resonances. The main aim of this work is to establish a theoretical framework for obtaining the spin-isospin transition strength at finite temperature and its extension to the description of stellar electron capture and β-decay. The nuclear ground state at finite temperature is determined by solving either the relativistic Hartree-Bogoliubov (FT-RHB) or Hartree Baarden-Cooper-Schrieffer (FT-HBCS) equations, while the relativistic quasiparticle random-phase approximation (FT-pnRQRPA) in the charge-exchange channel is developed to determine the excited states. The new theoretical approach combines the effects of nuclear pairing, finite temperature, and deformation. The limits of nuclear stability (drip lines) for hot nuclei are studied within the FT-RHB supplemented with the subtraction of continuum. Investigated spin-isospin excitations include the Fermi and Gamow-Teller (GT) transitions. While the Fermi transitions display one resonance peak independent of temperature and deformation, the GT transition strength has a much richer structure, more sensitive to the temperature and deformation effects. When considering the spherically symmetric nuclei, the GT strength separates into a low-lying, and a resonance region, as exemplified for even-even tin isotopes. However, the deformation effects lead to a substantial fragmentation of the GT transition strength, as demonstrated for selected pf-shell nuclei, exhibiting a crucial role of the nuclear shape. Results are presented for the EC rates of nuclei near the N = 50 shell closure, with subsequent implications for the supernovae simulations. The large-scale β-decay rate calculations are shown for even-even nuclei in the range 8 ≤ Z ≤ 82, displaying how the β-decay half-lives change with temperature and stellar density. Our study highlights the complex interplay between temperature, nuclear pairing, and deformation effects with subsequent implications for weak-interaction rates and their implementation in astrophysical models. Rad ne sadrži sažetak na drugom jeziku.

Electron capture on $^{20}$Ne is thought to play a crucial role in the final evolution of electron-degenerate ONe stellar cores. Recent calculations suggest that the capture process is dominated by the second-forbidden transition between the ground states of $^{20}$Ne and $^{20}$F, making an experimental determination of this transition strength highly desirable. To accomplish this task we are refurbishing an intermediate-image magnetic spectrometer capable of focusing 7 MeV electrons, and designing a scintillator detector surrounded by an active cosmic-ray veto shield, which will serve as an energy-dispersive device at the focal plane., 4 pages, 1 figure, NIC-XIV

R. Reifarth et al: ; 12 págs.; 9 figs.; Open Access funded by Creative Commons Atribution Licence 3.0 ; Nuclear Physics in Astrophysics VI (NPA6), The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process ow and r-process -decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will oer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes., This project was supported by the HGF Young Investigators Project VH-NG-327, EMMI, H4F, HGS-HIRe, JINA, NAVI, DFG and ATHENA.

Spin-isospin excitations of the medium-mass nucleus Co-58 were studied using the (n, p)-type (d,He-2) charge-exchange reaction at an incident energy E-d = 170 MeV and small scattering angles. The achieved energy resolution of 130 keV, full width at half maximum, allowed the extraction of Gamow-Teller strength to 13 peaks at excitation energies lower than 4.1 MeV in the residual nucleus Co-58 and is consistent with the results of a multipole-decomposition analysis. The identification of Gamow-Teller transitions is possible by comparison of the measured cross sections with DWBA calculations. The results are used to discuss the relevance of the Gamow-Teller strength distribution at low excitation energy with regard to electron-capture rates used in calculations for the final stage of a massive star. (C) 2003 Elsevier B.V. All rights reserved.

Gamow-Teller transitions in fp-shell nuclei have been studied using the 58 Ni( d , 2 He) charge exchange reaction at an incident energy of 170 MeV and forward angles. The measurements have been performed at AGOR using the Big-Bite Spectrometer and the EuroSuperNova focal-plane detection system. The unprecedented energy resolution of about 130 keV FWHM for excitations in the residual nucleus 58 Co allowed for the first time the extraction of single transitions in the β + direction up to about 4 MeV excitation. The impact on electron-capture rates in astrophysical environments has been evaluated.

Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states of T = 1, T-z = +/-1 nuclei to the common excited states of the T-z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT) transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T-z = 1 with those from the beta-decay of the T-z = -1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT transitions from Ni-58 (T-z = 1) to Cu-58 (T-z = 0) by using the zero-degree (He-3,t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified. The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., Dear to the Q window limitation (Q(EC) = 9.37 MeV) of the beta-decay from Zn-58 (T-z = -1) to Cu-58. The strength distribution is compared with that from shell-model calculations.

The proton-rich isotope Cu-56 was produced at the GSI On-Line Mass Separator by means of the Si-28(S-32, p3n) fusion-evaporation reaction. Its beta -decay properties were studied by detecting beta -delayed gamma rays and protons. A half-Life of 93 +/- 3 ms was determined for Cu-56. Compared to the previous work, six new gamma rays and three new levels were assigned to the daughter nucleus Ni-56. The measured Gamow-Teller strength values for five Ni-56 levels are compared to shell-model predictions. (C) 2001 Elsevier Science B.V. ALI rights reserved.

The Gamow-Teller strength for the transition from the ground state of (13)C to the T=1/2,J(pi)=3/2(-) excited state at 3.51 MeV in (13)N is extracted via the (13)C((3)He,t) reaction at 420 MeV. In contrast to results from earlier (p,n) studies on (13)C, a good agreement with shell-model calculations and the empirical unit cross-section systematics from other nuclei is found. The results are used to study the analog (13)N(e(-),nu(e))(13)C reaction, which plays a role in the pre-explosion convective phase of type Ia supernovae. Although the differences between the results from the ((3)He,t) and (p,n) data significantly affect the deduced electron-capture rate and the net heat deposition in the star resulting from this transition, the overall effect on the pre-explosive evolution is small.

The Gamow-Teller strength for the transition from the ground state of (13)C to the T=1/2,J(pi)=3/2(-) excited state at 3.51 MeV in (13)N is extracted via the (13)C((3)He,t) reaction at 420 MeV. In contrast to results from earlier (p,n) studies on (13)C, a good agreement with shell-model calculations and the empirical unit cross-section systematics from other nuclei is found. The results are used to study the analog (13)N(e(-),nu(e))(13)C reaction, which plays a role in the pre-explosion convective phase of type Ia supernovae. Although the differences between the results from the ((3)He,t) and (p,n) data significantly affect the deduced electron-capture rate and the net heat deposition in the star resulting from this transition, the overall effect on the pre-explosive evolution is small.

We introduce a novel theoretical framework for the description of weak interaction rates in reactions of leptons with finite nuclei. The weak interaction of leptons with hadrons is expressed in the standard current– current form, the nuclear ground state is described with the relativistic Hartree– Bogoliubov model and the relevant transitions to excited states are calculated in the relativistic quasiparticle random phase approximation. The model is tested for electron– and muon– neutrino reactions on 12C, in a study of cross sections averaged over experimental neutrino fluxes. Using 56Fe as an example, it is shown that at higher neutrino energies the inclusion of spin-dipole transitions, and also excitations of higher multipolarities, is essential for a quantitative description of neutrino– nucleus cross sections.

The Gamow-Teller strength for the transition from the ground state of 13C to the T=1/2, J^pi=3/2- excited state at 3.51 MeV in 13N is extracted via the 13C(3He,t) reaction at 420 MeV. In contrast to results from earlier (p,n) studies on 13C, a good agreement with shell-model calculations and the empirical unit cross section systematics from other nuclei is found. The results are used to study the analog 13N(e-,v_e)13C reaction, which plays a role in the pre-explosion convective phase of type Ia supernovae. Although the differences between the results from the (3He,t) and (p,n) data significantly affect the deduced electron-capture rate and the net heat-deposition in the star due to this transition, the overall effect on the pre-explosive evolution is small., 11 pages, 4 figures

It is shown via a study on a Mg-26 target that the (t,He-3) reaction at 115 MeV/nucleon reaction is an accurate probe for extracting Gamow-Teller transition strengths. To do so, the data are complemented by results from the Mg-26(He-3, t) reaction at 140 MeV/nucleon that allows for a comparison of T=2 analog states excited via the mirror reactions. Extracted Gamow-Teller strengths from Mg-26(t,He-3) and Mg-26(He-3, t) are compared with those from Mg-26(d,He-2) and Mg-26(p,n) studies, respectively. A good correspondence is found, indicating probe independence of the strength extraction. Furthermore, we test shell-model calculations using the new USD-05B interaction in the sd-model space and show that it reproduces the experimental Gamow-Teller strength distributions well. In anticipation of further (t,He-3) experiments on medium-heavy nuclei aimed at determining weak-interaction rates of relevance for stellar evolution, a second goal of this work is to improve the understanding of the (t,He-3) and (He-3, t) reaction mechanisms at intermediate energies because detailed studies are scarce. The distorted-wave Born approximation is employed, taking into account the composite structures of the He-3 and triton particles. The reaction model provides the means to explain systematic uncertainties at the 10%-20% level in the extraction of Gamow-Teller strengths as being because of interference between Gamow-Teller Delta L=0,Delta S=1 and Delta L=2,Delta S=1 amplitudes that both contribute to transitions from 0(+) to 1(+) states.

It is shown via a study on a Mg-26 target that the (t,He-3) reaction at 115 MeV/nucleon reaction is an accurate probe for extracting Gamow-Teller transition strengths. To do so, the data are complemented by results from the Mg-26(He-3, t) reaction at 140 MeV/nucleon that allows for a comparison of T=2 analog states excited via the mirror reactions. Extracted Gamow-Teller strengths from Mg-26(t,He-3) and Mg-26(He-3, t) are compared with those from Mg-26(d,He-2) and Mg-26(p,n) studies, respectively. A good correspondence is found, indicating probe independence of the strength extraction. Furthermore, we test shell-model calculations using the new USD-05B interaction in the sd-model space and show that it reproduces the experimental Gamow-Teller strength distributions well. In anticipation of further (t,He-3) experiments on medium-heavy nuclei aimed at determining weak-interaction rates of relevance for stellar evolution, a second goal of this work is to improve the understanding of the (t,He-3) and (He-3, t) reaction mechanisms at intermediate energies because detailed studies are scarce. The distorted-wave Born approximation is employed, taking into account the composite structures of the He-3 and triton particles. The reaction model provides the means to explain systematic uncertainties at the 10%-20% level in the extraction of Gamow-Teller strengths as being because of interference between Gamow-Teller Delta L=0,Delta S=1 and Delta L=2,Delta S=1 amplitudes that both contribute to transitions from 0(+) to 1(+) states.

The Gamow-Teller (GT) transition strengths in fp-shell nuclei are important parameters in presupernova models. A high-energy-resolution (He-3,t) experiment was performed on the T-z=1 nucleus Ti-46 at 0(degrees) and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final T-z=0 nucleus V-46. With an energy resolution of 33 keV, individual GT transitions were observed and GT strengths were derived for them up to the excitation energy of 4.5 MeV. The GT strengths were compared with shell-model calculations using various effective interactions. In this low-lying region, most GT states have isospin T=0. A few GT states with isospin T=1 were identified from the existence of the corresponding (analog) M1 states in Ti-46. By comparing the GT strength with the corresponding (analogous) M1 transition strength studied in Ti-46(e,e(')) or (gamma,gamma(')) measurements, a large constructive interference of orbital and spin terms was suggested for one of these M1 transitions.

Electron capture and beta decay play important roles in the evolution of presupernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in Co-58 from the Ni-58(t,He-3) reaction with a secondary triton beam of an intensity of similar to 10(6) pps at 115 MeV/nucleon and a resolution of similar to 250 keV. Previous measurements with the Ni-58(n,p) and the Ni-58(d,He-2) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell-model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from Ni-58(He-3, t) are described and turn out to be nonnegligible due to large interferences between the Delta L=0,Delta S=1 Gamow-Teller amplitude and the Delta L=2,Delta S=1 amplitude.

Electron capture and beta decay play important roles in the evolution of presupernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in Co-58 from the Ni-58(t,He-3) reaction with a secondary triton beam of an intensity of similar to 10(6) pps at 115 MeV/nucleon and a resolution of similar to 250 keV. Previous measurements with the Ni-58(n,p) and the Ni-58(d,He-2) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell-model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from Ni-58(He-3, t) are described and turn out to be nonnegligible due to large interferences between the Delta L=0,Delta S=1 Gamow-Teller amplitude and the Delta L=2,Delta S=1 amplitude.

Electron capture and beta decay play important roles in the evolution of presupernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in Co-58 from the Ni-58(t,He-3) reaction with a secondary triton beam of an intensity of similar to 10(6) pps at 115 MeV/nucleon and a resolution of similar to 250 keV. Previous measurements with the Ni-58(n,p) and the Ni-58(d,He-2) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell-model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from Ni-58(He-3, t) are described and turn out to be nonnegligible due to large interferences between the Delta L=0,Delta S=1 Gamow-Teller amplitude and the Delta L=2,Delta S=1 amplitude.

The Gamow-Teller (GT) transition strengths in fp -shell nuclei are important parameters in presupernova models. A high-energy-resolution ( 3 He ,t ) experiment was performed on the T z = 1 nucleus 46 Ti at 0 ◦ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final T z = 0 nucleus 46 V. With an energy resolution of 33 keV, individual GT transitions were observed and GT strengths were derived for them up to the excitation energy of 4.5 MeV. The GT strengths were compared with shell-model calculations using various effective interactions. In this low-lying region, most GT states have isospin T = 0. A few GT states with isospin T = 1 were identified from the existence of the corresponding (analog) M 1 states in 46 Ti. By comparing the GT strength with the corresponding (analogous) M 1 transition strength studied in 46 Ti( e, e )or( γ,γ ) measurements, a large constructive interference of orbital and spin terms was suggested for one of these M 1 transitions ispartof: Physical Review C, Nuclear Physics vol:73 issue:2 status: published

Cross sections for the charge-exchange reaction (d,He-2) on V-50, the only odd-odd stable nucleus in the pf shell, have been measured at an incident energy of 171 MeV. The two correlated protons of the unbound He-2 system were both momentum analyzed and detected by the same spectrometer and detector. Measurements have been carried out at forward center-of-mass angles up to 6degrees. The GT(+) strength distribution has been extracted up to about 12 MeV of excitation energy. Because charge-exchange reactions from V-50 provide a unique opportunity to probe Gamow-Teller response from an odd-odd nucleus of the pf shell, the present study serves as important test case for model calculations and astrophysical processes that proceed through GT-type transitions. Consequently, the experimental result is compared with a large-scale shell-model calculation, and the implications for electron-capture processes in presupernova environments are discussed.

Cross sections for the charge-exchange reaction (d,He-2) on V-50, the only odd-odd stable nucleus in the pf shell, have been measured at an incident energy of 171 MeV. The two correlated protons of the unbound He-2 system were both momentum analyzed and detected by the same spectrometer and detector. Measurements have been carried out at forward center-of-mass angles up to 6degrees. The GT(+) strength distribution has been extracted up to about 12 MeV of excitation energy. Because charge-exchange reactions from V-50 provide a unique opportunity to probe Gamow-Teller response from an odd-odd nucleus of the pf shell, the present study serves as important test case for model calculations and astrophysical processes that proceed through GT-type transitions. Consequently, the experimental result is compared with a large-scale shell-model calculation, and the implications for electron-capture processes in presupernova environments are discussed.

The excitation of isospin and spin-isospin modes has been a topic of much interest in the last two decades because of their importance to various astrophysical phenomena next to the intrinsic interest in their microscopic structure. (p, n) and other (p,n)-type reactions, such as (He-3,t), at intermediate energies have been used to map spin-isospin-flip strength in the beta(-) direction. For the beta(+) direction the spin-isospin-flip strength can, in principle, be mapped with the (n,p) reaction at intermediate energies. However, the resolution that can be obtained with secondary neutron beams is hardly useful to map accurately this strength. Better reactions could be (d, He-2) and (t,He-3) reactions at intermediate energies. Recently, at KVI a primary triton beam has been accelerated to energies of about 45 MeV/u. It is planned to use this beam to study isospin excitations in 'neutron-rich' nuclei. Furthermore, an unprecedented high resolution of 150 keV has been achieved with the (d,2He) reaction, which is a reaction of essentially pure spin- and isospin-flip character. This allows to map the spin-isospin strength and study its microscopic and multipole structure. Recent experimental results axe discussed.

The excitation of isospin and spin-isospin modes has been a topic of much interest in the last two decades because of their importance to various astrophysical phenomena next to the intrinsic interest in their microscopic structure. (p, n) and other (p,n)-type reactions, such as (He-3,t), at intermediate energies have been used to map spin-isospin-flip strength in the beta(-) direction. For the beta(+) direction the spin-isospin-flip strength can, in principle, be mapped with the (n,p) reaction at intermediate energies. However, the resolution that can be obtained with secondary neutron beams is hardly useful to map accurately this strength. Better reactions could be (d, He-2) and (t,He-3) reactions at intermediate energies. Recently, at KVI a primary triton beam has been accelerated to energies of about 45 MeV/u. It is planned to use this beam to study isospin excitations in 'neutron-rich' nuclei. Furthermore, an unprecedented high resolution of 150 keV has been achieved with the (d,2He) reaction, which is a reaction of essentially pure spin- and isospin-flip character. This allows to map the spin-isospin strength and study its microscopic and multipole structure. Recent experimental results axe discussed.

The excitation of isospin and spin-isospin modes has been a topic of much interest in the last two decades because of their importance to various astrophysical phenomena next to the intrinsic interest in their microscopic structure. (p, n) and other (p,n)-type reactions, such as (He-3,t), at intermediate energies have been used to map spin-isospin-flip strength in the beta(-) direction. For the beta(+) direction the spin-isospin-flip strength can, in principle, be mapped with the (n,p) reaction at intermediate energies. However, the resolution that can be obtained with secondary neutron beams is hardly useful to map accurately this strength. Better reactions could be (d, He-2) and (t,He-3) reactions at intermediate energies. Recently, at KVI a primary triton beam has been accelerated to energies of about 45 MeV/u. It is planned to use this beam to study isospin excitations in 'neutron-rich' nuclei. Furthermore, an unprecedented high resolution of 150 keV has been achieved with the (d,2He) reaction, which is a reaction of essentially pure spin- and isospin-flip character. This allows to map the spin-isospin strength and study its microscopic and multipole structure. Recent experimental results axe discussed.

The Mg-24(d,He-2)Na-24 and the C-12(d,He-2)B-12 charge-exchange reactions have been studied at an incident energy of 170 MeV. The two protons in the S-1(0)(pp) state (indicated as He-2) were both momentum analyzed and detected by the same spectrometer and detector. Background-free He-2 spectra with a resolution of about 150 keV (full width at half maximum) have been obtained allowing identification of many levels in the residual nucleus with high precision. It is found that the (d,He-2) reaction at 0degrees is largely governed by the Gamow-Teller (GT) transition operator for the beta(+) direction, which makes the reaction selective for isovector 1(+) transitions. In the case of Mg-24, the reaction is compared with (p,n) reaction data in which the same levels in the analog nucleus Al-24 are populated. Angular distributions of cross sections for the (d,He-2) reaction are presented and compared with distorted-wave Born approximation calculations. GT matrix elements are deduced. A level-by-level comparison with shell-model calculations using the universal s-d interaction has been performed. Comparison with (p,p(')) data yields a level scheme for the A=24 isospin triplet.

The Mg-24(d,He-2)Na-24 and the C-12(d,He-2)B-12 charge-exchange reactions have been studied at an incident energy of 170 MeV. The two protons in the S-1(0)(pp) state (indicated as He-2) were both momentum analyzed and detected by the same spectrometer and detector. Background-free He-2 spectra with a resolution of about 150 keV (full width at half maximum) have been obtained allowing identification of many levels in the residual nucleus with high precision. It is found that the (d,He-2) reaction at 0degrees is largely governed by the Gamow-Teller (GT) transition operator for the beta(+) direction, which makes the reaction selective for isovector 1(+) transitions. In the case of Mg-24, the reaction is compared with (p,n) reaction data in which the same levels in the analog nucleus Al-24 are populated. Angular distributions of cross sections for the (d,He-2) reaction are presented and compared with distorted-wave Born approximation calculations. GT matrix elements are deduced. A level-by-level comparison with shell-model calculations using the universal s-d interaction has been performed. Comparison with (p,p(')) data yields a level scheme for the A=24 isospin triplet.

Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states of T = 1, T-z = +/-1 nuclei to the common excited states of the T-z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT) transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T-z = 1 with those from the beta-decay of the T-z = -1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT transitions from Ni-58 (T-z = 1) to Cu-58 (T-z = 0) by using the zero-degree (He-3,t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified. The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., Dear to the Q window limitation (Q(EC) = 9.37 MeV) of the beta-decay from Zn-58 (T-z = -1) to Cu-58. The strength distribution is compared with that from shell-model calculations.

The Mg-24(d,He-2)Na-24 and the C-12(d,He-2)B-12 charge-exchange reactions have been studied at an incident energy of 170 MeV. The two protons in the S-1(0)(pp) state (indicated as He-2) were both momentum analyzed and detected by the same spectrometer and detector. Background-free He-2 spectra with a resolution of about 150 keV (full width at half maximum) have been obtained allowing identification of many levels in the residual nucleus with high precision. It is found that the (d,He-2) reaction at 0degrees is largely governed by the Gamow-Teller (GT) transition operator for the beta(+) direction, which makes the reaction selective for isovector 1(+) transitions. In the case of Mg-24, the reaction is compared with (p,n) reaction data in which the same levels in the analog nucleus Al-24 are populated. Angular distributions of cross sections for the (d,He-2) reaction are presented and compared with distorted-wave Born approximation calculations. GT matrix elements are deduced. A level-by-level comparison with shell-model calculations using the universal s-d interaction has been performed. Comparison with (p,p(')) data yields a level scheme for the A=24 isospin triplet.

The proton-rich isotope Cu-56 was produced at the GSI On-Line Mass Separator by means of the Si-28(S-32, p3n) fusion-evaporation reaction. Its beta -decay properties were studied by detecting beta -delayed gamma rays and protons. A half-Life of 93 +/- 3 ms was determined for Cu-56. Compared to the previous work, six new gamma rays and three new levels were assigned to the daughter nucleus Ni-56. The measured Gamow-Teller strength values for five Ni-56 levels are compared to shell-model predictions. (C) 2001 Elsevier Science B.V. ALI rights reserved.

Our collaboration has set up a focal plane detection system and a focal plane polarimeter at the large acceptance Big-Bite Spectrometer at AGOR. The detector systems are equipped with a high performance readout and online data processing system, which allows polarization transfer and charge transfer measurements at extreme forward angles with high precision. Preliminary results on GT+ strength distributions obtained in (d,2He) measurements revealing the fine structure of the distributions are presented. Their relation to recent calculations of stellar weak interaction rates is discussed., Comment: 8 pages, 4 figures, conference proceeding GR2000, Osaka, June 2000