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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 (96)Mo(d,(2)He)(96)Nb charge-exchange reaction was investigated at an incident energy of E(d)=183.5 MeV. An excitation-energy resolution of 110 keV was achieved. The experiment was performed at KVI, Groningen, using the magnetic spectrometer BBS at three angular positions: 0(degrees),2.5(degrees), and 6(degrees). We found that below 6 MeV almost the entire Gamow-Teller (GT(+)) strength is concentrated in a single state at 0.69 MeV excitation energy. As (96)Mo is the daughter of the beta beta decay nucleus (96)Zr, the present result provides information about the nuclear matrix elements active in the 2 nu beta beta decay of (96)Zr.

The (d,(2)He) charge-exchange reaction on (76)Se was studied at an incident energy of 183 MeV. The outgoing two protons in the (1)S(0) state, referred to as (2)He, were both momentum analyzed and detected by the same spectrometer and detector. The experiment was performed at KVI, Groningen, using the magnetic spectrometer BBS at three angular positions: 0(degrees),2.5(degrees), and 5(degrees). Excitation-energy spectra of the residual nucleus (76)As were obtained with an energy resolution of about 120 keV (FWHM). Gamow-Teller (GT(+)) transition strengths were extracted up to 5 MeV and compared with those from an (n,p) experiment at low resolution. Together with the GT(-) transition strengths from the (76)Ge(p,n) experiment leading to the same intermediate nucleus, the nuclear matrix element of the two-neutrino double-beta decay of (76)Ge was evaluated.

The (d,(2)He) charge-exchange reaction on (76)Se was studied at an incident energy of 183 MeV. The outgoing two protons in the (1)S(0) state, referred to as (2)He, were both momentum analyzed and detected by the same spectrometer and detector. The experiment was performed at KVI, Groningen, using the magnetic spectrometer BBS at three angular positions: 0(degrees),2.5(degrees), and 5(degrees). Excitation-energy spectra of the residual nucleus (76)As were obtained with an energy resolution of about 120 keV (FWHM). Gamow-Teller (GT(+)) transition strengths were extracted up to 5 MeV and compared with those from an (n,p) experiment at low resolution. Together with the GT(-) transition strengths from the (76)Ge(p,n) experiment leading to the same intermediate nucleus, the nuclear matrix element of the two-neutrino double-beta decay of (76)Ge was evaluated.

The (d,He-2) charge-exchange reaction on the double-beta decay (beta beta) nucleus Zn-64 has been studied at an incident energy of 183 MeV. The two protons in the S-1(0) state (indicated as He-2) were both momentum analyzed and detected simultaneously by the BBS magnetic spectrometer and its position-sensitive detector. He-2 spectra with a resolution of about 115 keV (FWHM) have been obtained allowing identification of many levels in the residual nucleus Cu-64 with high precision. Zn-64 is one of the rare cases undergoing a beta beta decay in beta(+) direction. In the experiment presented here, Gamow-Teller (GT(+)) transition strengths have been extracted. Together with the GT(-) transition strengths from Ni-64(He-3,t) data to the same intermediate nucleus Cu-64, the nuclear matrix elements of the beta beta decay of Zn-64 have been evaluated. Finally, the GT(+/-) distributions are compared with shell-model calculations and a critical assessment is given of the various residual interactions presently employed for the pf shell.

The two-neutrino double-beta (2nubetabeta) decay represents a test case for our knowledge about the nuclear structure of the involved isobars. The decay of Ca-48 is an especially interesting case because it holds an anomaly of a uniquely high Q(betabeta) value and a comparatively long half-life, which points to a peculiar nuclear structure situation. The nuclear matrix element relevant for betabeta decay can be calculated, if the complete set of Gamow-Teller (GT) matrix elements for the two virtual transitions in the perturbative description are known. Using the high-resolution (d, He-2) probe, we have measured the GT(+) strength distribution in Sc-48, which is the intermediate nucleus in the Ca-48 betabeta decay. By combining our measured GT distribution with data from a Ca-48(p, n) experiment and taking into account relative phases between individual matrix elements, which can be gained from theoretical models, one can compute the double-GT matrix element and deduce the half-life of the Ca-48 2nubetabeta decay.

The two-neutrino double-beta (2nubetabeta) decay represents a test case for our knowledge about the nuclear structure of the involved isobars. The decay of Ca-48 is an especially interesting case because it holds an anomaly of a uniquely high Q(betabeta) value and a comparatively long half-life, which points to a peculiar nuclear structure situation. The nuclear matrix element relevant for betabeta decay can be calculated, if the complete set of Gamow-Teller (GT) matrix elements for the two virtual transitions in the perturbative description are known. Using the high-resolution (d, He-2) probe, we have measured the GT(+) strength distribution in Sc-48, which is the intermediate nucleus in the Ca-48 betabeta decay. By combining our measured GT distribution with data from a Ca-48(p, n) experiment and taking into account relative phases between individual matrix elements, which can be gained from theoretical models, one can compute the double-GT matrix element and deduce the half-life of the Ca-48 2nubetabeta decay.