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A Ga-71(He-3,t)Ge-71 charge-exchange experiment was performed to extract with high precision the Gamow-Teller (GT) transition strengths to the three lowest-lying states in Ge-71, i.e., the ground state (1/2(-)), the 175 keV (5/2(-)) and the 500 key (3/2(-)) excited states. These are the relevant states, which are populated via a charged-current reaction induced by neutrinos from reactor-produced Cr-51 and Ar-37 sources. A precise measurement of the GT transition strengths is an important input into the calibration of the SAGE and GALLEX solar neutrino detectors and addresses a long-standing discrepancy between the measured and evaluated capture rates from the Cr-51 and Ar-37 neutrino calibration sources, which has recently spawned new ideas about unconventional neutrino properties. (C) 2011 Elsevier B.V. All rights reserved.

A Ga-71(He-3,t)Ge-71 charge-exchange experiment was performed to extract with high precision the Gamow-Teller (GT) transition strengths to the three lowest-lying states in Ge-71, i.e., the ground state (1/2(-)), the 175 keV (5/2(-)) and the 500 key (3/2(-)) excited states. These are the relevant states, which are populated via a charged-current reaction induced by neutrinos from reactor-produced Cr-51 and Ar-37 sources. A precise measurement of the GT transition strengths is an important input into the calibration of the SAGE and GALLEX solar neutrino detectors and addresses a long-standing discrepancy between the measured and evaluated capture rates from the Cr-51 and Ar-37 neutrino calibration sources, which has recently spawned new ideas about unconventional neutrino properties. (C) 2011 Elsevier B.V. All rights reserved.

A precision measurement of the Ga-71(He-3,t)Ge-71 charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective neutron-separation energy in Ge-71 was extracted. The data and the analysis constrain the Ga-71(nu(e),e(-)) solar neutrino rate in a neutrino nonoscillation scenario. For nonoscillating neutrinos we report a solar neutrino capture rate of 122.4 +/- 3.4(stat) +/- 1.1(sys) SNU, which is lower than the presently accepted value of 132 +/- 18 SNU, though not in disagreement given the quoted errors.

A precision measurement of the Ga-71(He-3,t)Ge-71 charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective neutron-separation energy in Ge-71 was extracted. The data and the analysis constrain the Ga-71(nu(e),e(-)) solar neutrino rate in a neutrino nonoscillation scenario. For nonoscillating neutrinos we report a solar neutrino capture rate of 122.4 +/- 3.4(stat) +/- 1.1(sys) SNU, which is lower than the presently accepted value of 132 +/- 18 SNU, though not in disagreement given the quoted errors.

A precision measurement of the Ga-71(He-3,t)Ge-71 charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective neutron-separation energy in Ge-71 was extracted. The data and the analysis constrain the Ga-71(nu(e),e(-)) solar neutrino rate in a neutrino nonoscillation scenario. For nonoscillating neutrinos we report a solar neutrino capture rate of 122.4 +/- 3.4(stat) +/- 1.1(sys) SNU, which is lower than the presently accepted value of 132 +/- 18 SNU, though not in disagreement given the quoted errors.

The two charge exchange reactions 14N(d, 2He)14C and 14N(3He, t)14O were studied with high resolution in order to identify the Gamow–Teller (GT) strength distribution starting from the ground state (g.s.) of 14N in the β− and β+ directions. The isospin symmetry in the A = 14 mass system is investigated. An overview of the main features of the experimental investigation is summarized here.

The excitation and subsequent decay by proton emission of the isovector spin-flip giant monopole resonance are studied via the Pb-208 (He-3, t) reaction at 410 MeV. In the tritonsingles spectrum 60 +/- 5% of the non-energy-weighted sum-rule strength for this 2hw resonance is found in the region 29

The isoscalar giant monopole resonance (ISGMR) in even-A Cd isotopes has been studied by inelastic ${\alpha}$-scattering at 100 MeV/u and at extremely forward angles, including 0deg. The asymmetry term in the nuclear incompressibility extracted from the ISGMR in Cd isotopes is found to be $K_{\tau} = -555 \pm 75$ MeV, confirming the value previously obtained from the Sn isotopes. ISGMR strength has been computed in relativistic RPA using NL3 and FSUGold effective interactions. Both models significantly overestimate the centroids of the ISGMR strength in the Cd isotopes. Combined with other recent theoretical effort, the question of the "softness" of the open-shell nuclei in the tin region remains open still., Comment: Minor changes in text. Scaling energies added to Table I. 5 pages (2-column format), 4 figures

A Ga-71(He-3,t)Ge-71 charge-exchange experiment was performed to extract with high precision the Gamow-Teller (GT) transition strengths to the three lowest-lying states in Ge-71, i.e., the ground state (1/2(-)), the 175 keV (5/2(-)) and the 500 key (3/2(-)) excited states. These are the relevant states, which are populated via a charged-current reaction induced by neutrinos from reactor-produced Cr-51 and Ar-37 sources. A precise measurement of the GT transition strengths is an important input into the calibration of the SAGE and GALLEX solar neutrino detectors and addresses a long-standing discrepancy between the measured and evaluated capture rates from the Cr-51 and Ar-37 neutrino calibration sources, which has recently spawned new ideas about unconventional neutrino properties. (C) 2011 Elsevier B.V. All rights reserved.

A (He-3, t) charge-exchange reaction experiment on the double-beta decaying nucleus Xe-136 has been performed at an incident energy of 420 MeV with the objective to measure the Gamow-Teller (GT) strength distribution in Cs-136. The measurements have been carried out at the dispersion-matched WS beam line and the Grand Raiden spectrometer of the Research Center for Nuclear Physics in Osaka, where an energy resolution of 42 keV was achieved. A new gas cell with thin windows made of polyethylene naphthalate has been employed as a target. The extracted GT strength distribution is confronted with the rather long 2 nu beta beta decay half-life of Xe-136.

A (He-3, t) charge-exchange reaction experiment on the double-beta decaying nucleus Xe-136 has been performed at an incident energy of 420 MeV with the objective to measure the Gamow-Teller (GT) strength distribution in Cs-136. The measurements have been carried out at the dispersion-matched WS beam line and the Grand Raiden spectrometer of the Research Center for Nuclear Physics in Osaka, where an energy resolution of 42 keV was achieved. A new gas cell with thin windows made of polyethylene naphthalate has been employed as a target. The extracted GT strength distribution is confronted with the rather long 2 nu beta beta decay half-life of Xe-136.

A (He-3, t) charge-exchange reaction experiment on the double-beta decaying nucleus Xe-136 has been performed at an incident energy of 420 MeV with the objective to measure the Gamow-Teller (GT) strength distribution in Cs-136. The measurements have been carried out at the dispersion-matched WS beam line and the Grand Raiden spectrometer of the Research Center for Nuclear Physics in Osaka, where an energy resolution of 42 keV was achieved. A new gas cell with thin windows made of polyethylene naphthalate has been employed as a target. The extracted GT strength distribution is confronted with the rather long 2 nu beta beta decay half-life of Xe-136.

The Nd-150(3He,t) reaction at 140 MeV/u and Sm-150(t,He-3) reaction at 115 MeV/u were measured, populating excited states in Pm-150. The transitions studied populate intermediate states of importance for the (neutrinoless) beta beta decay of Nd-150 to Sm-150. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless beta beta decay (0 nu beta beta) of Nd-150. The present results thus provide useful information on the neutrino responses for evaluating the 0 nu beta beta and 2 nu beta beta matrix elements. The 2 nu beta beta matrix element calculated from the Gamow-Teller transitions through the lowest 1(+) state in the intermediate nucleus is maximally about half that deduced from the half-life measured in 2 nu beta beta direct counting experiments, and at least several transitions through 1+ intermediate states in Pm-150 are required to explain the 2 nu beta beta half-life. Because Gamow-Teller transitions in the Sm-150(t,3He) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the 2 (h) over bar omega, Lambda L = 0, Delta S = 1 isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

The Nd-150(3He,t) reaction at 140 MeV/u and Sm-150(t,He-3) reaction at 115 MeV/u were measured, populating excited states in Pm-150. The transitions studied populate intermediate states of importance for the (neutrinoless) beta beta decay of Nd-150 to Sm-150. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless beta beta decay (0 nu beta beta) of Nd-150. The present results thus provide useful information on the neutrino responses for evaluating the 0 nu beta beta and 2 nu beta beta matrix elements. The 2 nu beta beta matrix element calculated from the Gamow-Teller transitions through the lowest 1(+) state in the intermediate nucleus is maximally about half that deduced from the half-life measured in 2 nu beta beta direct counting experiments, and at least several transitions through 1+ intermediate states in Pm-150 are required to explain the 2 nu beta beta half-life. Because Gamow-Teller transitions in the Sm-150(t,3He) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the 2 (h) over bar omega, Lambda L = 0, Delta S = 1 isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

The Nd-150(3He,t) reaction at 140 MeV/u and Sm-150(t,He-3) reaction at 115 MeV/u were measured, populating excited states in Pm-150. The transitions studied populate intermediate states of importance for the (neutrinoless) beta beta decay of Nd-150 to Sm-150. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless beta beta decay (0 nu beta beta) of Nd-150. The present results thus provide useful information on the neutrino responses for evaluating the 0 nu beta beta and 2 nu beta beta matrix elements. The 2 nu beta beta matrix element calculated from the Gamow-Teller transitions through the lowest 1(+) state in the intermediate nucleus is maximally about half that deduced from the half-life measured in 2 nu beta beta direct counting experiments, and at least several transitions through 1+ intermediate states in Pm-150 are required to explain the 2 nu beta beta half-life. Because Gamow-Teller transitions in the Sm-150(t,3He) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the 2 (h) over bar omega, Lambda L = 0, Delta S = 1 isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus Mg-22 by measuring the Mg-24(p,t)Mg-22 reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of alpha-unbound states was identified and precise excitation energies were determined. Based on shell model and alpha-cluster model calculations we predict the level parameters for determining the stellar reaction rate of Ne-18(alpha,p)Na-21 for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.

x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus Mg-22 by measuring the Mg-24(p,t)Mg-22 reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of alpha-unbound states was identified and precise excitation energies were determined. Based on shell model and alpha-cluster model calculations we predict the level parameters for determining the stellar reaction rate of Ne-18(alpha,p)Na-21 for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.

x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus Mg-22 by measuring the Mg-24(p,t)Mg-22 reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of alpha-unbound states was identified and precise excitation energies were determined. Based on shell model and alpha-cluster model calculations we predict the level parameters for determining the stellar reaction rate of Ne-18(alpha,p)Na-21 for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.

13 pages, 15 figures.-- Printed version published Jul 1, 2009., Measurements of inelastic proton scattering with high energy resolution at forward scattering angles including 0 degrees are described. High-resolution halo-free beams were accelerated by the cyclotron complex at the Research Center for Nuclear Physics. Instrumental background events were minimized using the high-quality beam. The remaining instrumental background events were eliminated by applying a background subtraction method. As a result, clean spectra were obtained even for a heavy target nucleus such as Pb-208. A high energy resolution of 20 keV (FWHM) and a scattering angle resolution of +/- 0.6 degrees were achieved at an incident proton energy of 295 MeV. (C) 2009 Elsevier B.V. All rights reserved., This work has been partly supported by the Grants-in Aid for Scientific Research no. 14740154 and 18540270 of the Ministry of Education, Culture, Sports, Science and Technology of Japan.

To study the Gamow-Teller (GT) transitions to the pf-shell nucleus Cu-64, the Ni-64(He-3,t)Cu-64 experiment was performed at the Research Center for Nuclear Physics (RCNP) Ring Cyclotron, Osaka, using a He-3 beam of 140 MeV/nucleon. The outgoing tritons were momentum analyzed by the Grand Raiden spectrometer at 0(degrees). A high energy resolution of 32 keV (full width at half-maximum) allowed the separation of individual levels in the excitation-energy region from 0 to 3.5 MeV. In addition to the ground state (gs), known to be a J(pi)=1(+) GT state, many low-lying states showed L=0 nature, suggesting that they are candidates for GT states. Because the GT strength B(GT) for the gs transition is known from the beta-decay measurement, the strengths for the excited states could be determined using the proportionality between the B(GT) and the reaction cross section extrapolated to q=0 momentum transfer. At higher excitation energies, the level density becomes high and the so-called GT giant resonance dominates the spectrum. The lower and the upper limits of the strength contained in this energy region were estimated. Our results show that less than 55% of the strength predicted by the Ikeda sum rule is located in the excitation-energy region from 0 to 17 MeV..

To study the Gamow-Teller (GT) transitions to the pf-shell nucleus Cu-64, the Ni-64(He-3,t)Cu-64 experiment was performed at the Research Center for Nuclear Physics (RCNP) Ring Cyclotron, Osaka, using a He-3 beam of 140 MeV/nucleon. The outgoing tritons were momentum analyzed by the Grand Raiden spectrometer at 0(degrees). A high energy resolution of 32 keV (full width at half-maximum) allowed the separation of individual levels in the excitation-energy region from 0 to 3.5 MeV. In addition to the ground state (gs), known to be a J(pi)=1(+) GT state, many low-lying states showed L=0 nature, suggesting that they are candidates for GT states. Because the GT strength B(GT) for the gs transition is known from the beta-decay measurement, the strengths for the excited states could be determined using the proportionality between the B(GT) and the reaction cross section extrapolated to q=0 momentum transfer. At higher excitation energies, the level density becomes high and the so-called GT giant resonance dominates the spectrum. The lower and the upper limits of the strength contained in this energy region were estimated. Our results show that less than 55% of the strength predicted by the Ikeda sum rule is located in the excitation-energy region from 0 to 17 MeV..

To study the Gamow-Teller (GT) transitions to the pf-shell nucleus Cu-64, the Ni-64(He-3,t)Cu-64 experiment was performed at the Research Center for Nuclear Physics (RCNP) Ring Cyclotron, Osaka, using a He-3 beam of 140 MeV/nucleon. The outgoing tritons were momentum analyzed by the Grand Raiden spectrometer at 0(degrees). A high energy resolution of 32 keV (full width at half-maximum) allowed the separation of individual levels in the excitation-energy region from 0 to 3.5 MeV. In addition to the ground state (gs), known to be a J(pi)=1(+) GT state, many low-lying states showed L=0 nature, suggesting that they are candidates for GT states. Because the GT strength B(GT) for the gs transition is known from the beta-decay measurement, the strengths for the excited states could be determined using the proportionality between the B(GT) and the reaction cross section extrapolated to q=0 momentum transfer. At higher excitation energies, the level density becomes high and the so-called GT giant resonance dominates the spectrum. The lower and the upper limits of the strength contained in this energy region were estimated. Our results show that less than 55% of the strength predicted by the Ikeda sum rule is located in the excitation-energy region from 0 to 17 MeV..

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.

Differential cross sections for transitions of known weak strength were measured with the (He-3, t) reaction at 420 MeV on targets of C-12, C-13, O-18, Mg-26, Ni-58, Ni-60, Zr-90, Sn-118, Sn-120, and Pb-208. Using these data, it is shown that the proportionalities between strengths and cross sections for this probe follow simple trends as a function of mass number. These trends can be used to confidently determine Gamow-Teller strength distributions in nuclei for which the proportionality cannot be calibrated via beta-decay strengths. Although theoretical calculations in the distorted-wave Born approximation overestimate the data, they allow one to understand the main experimental features and to predict deviations from the simple trends observed in some of the transitions.

Differential cross sections for transitions of known weak strength were measured with the (He-3, t) reaction at 420 MeV on targets of C-12, C-13, O-18, Mg-26, Ni-58, Ni-60, Zr-90, Sn-118, Sn-120, and Pb-208. Using these data, it is shown that the proportionalities between strengths and cross sections for this probe follow simple trends as a function of mass number. These trends can be used to confidently determine Gamow-Teller strength distributions in nuclei for which the proportionality cannot be calibrated via beta-decay strengths. Although theoretical calculations in the distorted-wave Born approximation overestimate the data, they allow one to understand the main experimental features and to predict deviations from the simple trends observed in some of the transitions.

Differential cross sections for transitions of known weak strength were measured with the (He-3, t) reaction at 420 MeV on targets of C-12, C-13, O-18, Mg-26, Ni-58, Ni-60, Zr-90, Sn-118, Sn-120, and Pb-208. Using these data, it is shown that the proportionalities between strengths and cross sections for this probe follow simple trends as a function of mass number. These trends can be used to confidently determine Gamow-Teller strength distributions in nuclei for which the proportionality cannot be calibrated via beta-decay strengths. Although theoretical calculations in the distorted-wave Born approximation overestimate the data, they allow one to understand the main experimental features and to predict deviations from the simple trends observed in some of the transitions.

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.

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.

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.

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

Isospin symmetry is expected for the T-z=+/- 1 -> 0 isobaric analogous transitions in isobars with mass number A, where T-z is the z component of isospin T. Assuming this symmetry, strengths of analogous Gamow-Teller (GT) transitions within A=50 isobars were determined from a high energy-resolution T-z=+1 -> 0, Cr-50(He-3,t)Mn-50 study at 0 degrees in combination with the decay Q value and lifetime from the T-z=-1 -> 0, Fe-50 ->Mn-50 beta decay. This method can be applied to other pf-shell nuclei and can be used to study GT strengths of astrophysical interest.

A C-14(He-3,t)O-14 experiment was performed using a He-3 beam with E=140 MeV/nucleon. The achieved resolution of 33 keV (full width at half maximum) for the small scattering angle spectrum allowed the determination of the widths of several levels up to an excitation energy of 11.5 MeV. The width of the E-x=5.17 MeV,J(pi)=1(-) level was in good agreement with the known value, while for other states considerably improved or new results were obtained.

A C-14(He-3,t)O-14 experiment was performed using a He-3 beam with E=140 MeV/nucleon. The achieved resolution of 33 keV (full width at half maximum) for the small scattering angle spectrum allowed the determination of the widths of several levels up to an excitation energy of 11.5 MeV. The width of the E-x=5.17 MeV,J(pi)=1(-) level was in good agreement with the known value, while for other states considerably improved or new results were obtained.

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A. The, strengths of T-z = +/-3/2 --> 1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A = 41 isobar quartet are compared in detail. The T-z = +3/2 --> +1/2 GT transitions from the J(pi) = 3/2(+) ground state of K-41 leading to excited J(pi) = 1/2(+), 3/2(+), and 5/2(+) states in Ca-41 were measured using the (He-3, t) charge-exchange reaction. With a high energy resolution of 35 keV, many fragmented states were observed, and the GT strength distribution was determined up to 10 MeV excitation energy (E-x). The main part of the strength was concentrated in the E-x = 4-6 MeV region. A shell-model calculation could reproduce the concentration, but not so well details of the strength distribution. The obtained distribution was further compared with two results of Ti-41 beta decay studying the analogous T-z = -3/2 --> -1/2 GT strengths. They reported contradicting distributions. One-to-one correspondences of analogous transitions and analog states were assigned up to E-x = 6 MeV in the comparison with one of these Ti-41 beta-decay results. Combining the spectroscopic information of the analog states in Ca-41 and Sc-41, the most probable J(pi) values were deduced for each pair of analog states. It was found that 5/2(+) states carry the main part of the observed GT strength, while much less GT strength was carried by 1/2(+) and 3/2(+) states. The gross features of the GT strength distributions for each J were similar for the isospin analogous T-z = +/-3/2 --> +/-1/2 transitions, but the details were somewhat different. From the difference of the distributions, isospin-asymmetry matrix elements of 8 keV were deduced. The Coulomb displacement energy, which is sensitive to the configuration of states, showed a sudden increase of about 50 keV at the excitation energy of 3.8 MeV. The strengths of several M1 transitions to the IAS in Ca-41 were compared with the strengths of analogous GT transitions. It was found that ratios of the M1 and GT transition strengths were similar, suggesting that the contributions of the ltau term in M1 transitions are small.

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A. The, strengths of T-z = +/-3/2 --> 1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A = 41 isobar quartet are compared in detail. The T-z = +3/2 --> +1/2 GT transitions from the J(pi) = 3/2(+) ground state of K-41 leading to excited J(pi) = 1/2(+), 3/2(+), and 5/2(+) states in Ca-41 were measured using the (He-3, t) charge-exchange reaction. With a high energy resolution of 35 keV, many fragmented states were observed, and the GT strength distribution was determined up to 10 MeV excitation energy (E-x). The main part of the strength was concentrated in the E-x = 4-6 MeV region. A shell-model calculation could reproduce the concentration, but not so well details of the strength distribution. The obtained distribution was further compared with two results of Ti-41 beta decay studying the analogous T-z = -3/2 --> -1/2 GT strengths. They reported contradicting distributions. One-to-one correspondences of analogous transitions and analog states were assigned up to E-x = 6 MeV in the comparison with one of these Ti-41 beta-decay results. Combining the spectroscopic information of the analog states in Ca-41 and Sc-41, the most probable J(pi) values were deduced for each pair of analog states. It was found that 5/2(+) states carry the main part of the observed GT strength, while much less GT strength was carried by 1/2(+) and 3/2(+) states. The gross features of the GT strength distributions for each J were similar for the isospin analogous T-z = +/-3/2 --> +/-1/2 transitions, but the details were somewhat different. From the difference of the distributions, isospin-asymmetry matrix elements of 8 keV were deduced. The Coulomb displacement energy, which is sensitive to the configuration of states, showed a sudden increase of about 50 keV at the excitation energy of 3.8 MeV. The strengths of several M1 transitions to the IAS in Ca-41 were compared with the strengths of analogous GT transitions. It was found that ratios of the M1 and GT transition strengths were similar, suggesting that the contributions of the ltau term in M1 transitions are small.

A high energy-resolution B-11 (He-3,t)C-11 experiment was performed at 0degrees and an intermediate incident energy of 140 MeV/nucleon for the study of precise Gamow-Teller (GT) transition strengths. Two doublet states at approximate to4.5 and approximate to8.4 MeV were clearly resolved with a resolution of 45 keV. The strengths are compared with a calculation using an ab initio no-core shell model, which became available for the A=11 system recently. It was found that a calculation including a three-nucleon interaction better reproduces the observed GT transition strengths.

A high energy-resolution B-11 (He-3,t)C-11 experiment was performed at 0degrees and an intermediate incident energy of 140 MeV/nucleon for the study of precise Gamow-Teller (GT) transition strengths. Two doublet states at approximate to4.5 and approximate to8.4 MeV were clearly resolved with a resolution of 45 keV. The strengths are compared with a calculation using an ab initio no-core shell model, which became available for the A=11 system recently. It was found that a calculation including a three-nucleon interaction better reproduces the observed GT transition strengths.

A high energy-resolution B-11 (He-3,t)C-11 experiment was performed at 0degrees and an intermediate incident energy of 140 MeV/nucleon for the study of precise Gamow-Teller (GT) transition strengths. Two doublet states at approximate to4.5 and approximate to8.4 MeV were clearly resolved with a resolution of 45 keV. The strengths are compared with a calculation using an ab initio no-core shell model, which became available for the A=11 system recently. It was found that a calculation including a three-nucleon interaction better reproduces the observed GT transition strengths.

After 50 years of its prediction, the highest-lying [2 0 2]3/2 orbit among the six Nilsson single-particle orbits originating from the sd shells in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5 MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0degrees having a strong selectivity for Gamow-Teller transitions. In the comparison with the analogous M1 transitions in Mg-25, the J(pi)=3/2(+) bandhead state and the excited 5/2(+) and 7/2(+) members were clearly assigned.

After 50 years of its prediction, the highest-lying [2 0 2]3/2 orbit among the six Nilsson single-particle orbits originating from the sd shells in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5 MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0degrees having a strong selectivity for Gamow-Teller transitions. In the comparison with the analogous M1 transitions in Mg-25, the J(pi)=3/2(+) bandhead state and the excited 5/2(+) and 7/2(+) members were clearly assigned.

After 50 years of its prediction, the highest-lying [2 0 2]3/2 orbit among the six Nilsson single-particle orbits originating from the sd shells in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5 MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0degrees having a strong selectivity for Gamow-Teller transitions. In the comparison with the analogous M1 transitions in Mg-25, the J(pi)=3/2(+) bandhead state and the excited 5/2(+) and 7/2(+) members were clearly assigned.