Proefschrift--Utrecht. / "Stellingen": [4] p. inserted. Includes bibliographies.

No description available.

Motivated by existing nuclear astrophysics problems, the B-decay of the proton rich nucleus 23Al was studied for the first time with pure samples which were obtained by using the 1H(24Mg,23Al)2n reaction and the MARS recoil separator at Texas A&M University. B and B-y coincidence measurements were made with a fast tape-transport system, scintillator, BGO and HPGe y detectors. The experiment allowed us to measure absolute B branching ratios and to determine logft values for transitions to final states in 23Mg, including the isobaric analog state (IAS), and, therefore, to determine unambiguously the spin and parity of the 23Al ground state to be J^Pi = 5/2+. This work excludes the large increases in the radiative proton capture cross section for the reaction 22Mg(p, )23Al at astrophysical energies, which were implied by claims that the spin and parity of the 23Al ground state were J^Pi = 1/2+. More precise half life and mass determinations of 23Al were obtained from the experimental data. The logft for the Fermi transition to its isobaric analog state in 23Mg was also determined for the first time. This IAS and a state 16 keV below it were observed, well separated in the same experiment for the first time. The B-decay scheme of the proton rich nucleus 23Al was established. We can now solve a number of inconsistencies in the literature, exclude strong isospin mixing claimed before, and obtain a new determination of the resonance strength. The IAS and the state 16 keV below it are resonances in the 22Na(p, )23 Mg reaction at energies that are important in novae. This second state turns out to be the resonance that gives the most important contribution in the depletion of 22Na from novae. Both of the reactions of 22Mg(p, )23Al and 22Na(p, )23Mg have been suggested as possible candidates for diverting some of the flux in oxygen-neon novae explosions from the A=22 into the A=23 mass chain.

Using the NEMO-3 detector, 410.4 g of ¹¹⁶Cd with a total exposure of 1.65 kg• y and 932 g of ⁸²Se with a total exposure of 3.75 kg• y were used to measure the half-life of two-neutrino double beta decay (2[nu][beta][beta]) to the ground states of ¹¹⁶Sn and ⁸²Kr and to place a lower limit on the neutrinoless double becay decay (0[nu][beta][beta]) to the same ground states. Under the single-states dominance hypothesis, the 2[nu][beta][beta] half-lives are found to be T 1/2(¹¹⁶Cd) = (2.90 ± 0.03(stat) ± 0.15(syst)×10¹⁹ yr and T 1/2(⁸²Se) = [10.62±0.11(stat)±0.56(syst)]×10¹⁹ yr. 0[nu][beta][beta] is excluded to 90% confidence level at T 1/2 ≥ 1.12 × 10²³ yr for ¹¹⁶Cd and T 1/2 ≥ 3.90 × 10²³ yr for ⁸²Se. These half-lives correspond to effective Majorana neutrino masses of m ≤ (4.33 - 5.54) eV and m ≤ (2.28 - 2.82) eV, respectively, in the light Majorana exchange mechanism. / text

No description available.

No description available.

In light of present (EXO) and future (BOREXINO & XMASS) projects searching for evidence of the, as yet, unobserved double-beta decay of 136Xe, an atomic mass difference of 136Xe – 136Ba was determined using the high-precision Manitoba II mass spectrometer at the University of Manitoba. The Q-value for this difference was determined to be 2458.72(56) keV. The double-beta decay mode can be either neutrino (ββ2υ) or neutrinoless (ββ0υ), where the latter would be proof of the Majorana nature of neutrinos. A ββ0υ decay, which violates several principles of the Standard Model of particle physics, would emit only electrons and would provide a defined peak at the Q-value for the decay. This decay would also require the Majorana neutrino to have a non-zero rest mass and be its own antiparticle. Results of mass measurements on mass doublets of 135Ba, 136Ba, 137Ba, and 138Ba will be given. An improved measurement of the 116Cd35Cl - 114Cd37Cl doublet, previously done by Meredith et al. in 1973, will also be given.

Graduate

In light of present (EXO) and future (BOREXINO & XMASS) projects searching for evidence of the, as yet, unobserved double-beta decay of 136Xe, an atomic mass difference of 136Xe – 136Ba was determined using the high-precision Manitoba II mass spectrometer at the University of Manitoba. The Q-value for this difference was determined to be 2458.72(56) keV. The double-beta decay mode can be either neutrino (ββ2υ) or neutrinoless (ββ0υ), where the latter would be proof of the Majorana nature of neutrinos. A ββ0υ decay, which violates several principles of the Standard Model of particle physics, would emit only electrons and would provide a defined peak at the Q-value for the decay. This decay would also require the Majorana neutrino to have a non-zero rest mass and be its own antiparticle. Results of mass measurements on mass doublets of 135Ba, 136Ba, 137Ba, and 138Ba will be given. An improved measurement of the 116Cd35Cl - 114Cd37Cl doublet, previously done by Meredith et al. in 1973, will also be given.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 157-166).