Modeling the composition of neutron-star crusts depends strongly on binding energies of neutron-rich nuclides near the N ¼ 50 and N ¼ 82 shell closures. Using a recent development of time-of-flight mass spectrometry for on-line purification of radioactive ion beams to access more exotic species, we have determined for the first time the mass of 82 Zn with the ISOLTRAP setup at the ISOLDE-CERN facility. With a robust neutron-star model based on nuclear energy-density-functional theory, we solve the general relativistic Tolman-Oppenheimer-Volkoff equations and calculate the neutron-star crust composition based on the new experimental mass. The composition profile is not only altered but now constrained by experimental data deeper into the crust than before.

No abstract

Mass measurements of 96;97 Kr using the ISOLTRAP Penning-trap spectrometer at CERN-ISOLDE are reported, extending the mass surface beyond N ¼ 60 for Z ¼ 36. These new results show behavior in sharp contrast to the heavier neighbors where a sudden and intense deformation is present. We interpret this as the establishment of a nuclear quantum phase transition critical-point boundary. The new masses confirm findings from nuclear mean-square charge-radius measurements up to N ¼ 60 but are at variance with conclusions from recent gamma-ray spectroscopy. DOI: 10.1103/PhysRevLett.105.032502 PACS numbers: 21.10.Dr, 64.70.Tg, 74.40.Kb Dynamical symmetries are an enlightening paradigm for describing the stucture of matter. Iachello and Arima have elegantly described the application of dynamic symmetries in nuclear physics by developing the Interacting Boson Model (IBM) [1]. The IBM allowed the classification of nuclear spectra in terms of U(6) group theory and predicted the occurrence of three dynamical symmetries: U(5), SU(3), and SO(6) [2]. More recent attempts to enlarge these concepts have resulted in the elaboration of criticalpoint symmetries, notably for nuclear shapes [3,4]. These are particularly interesting since they apply to interactions that are discontinuous and describe phenomena in terms of quantum phase transitions. Whereas classical phase transitions follow changes in temperature and pressure, the quantum phase transitions of nuclear shapes occur when neutrons and protons change their orbit occupation in the nucleus.The IBM formalism describes the ground-state band of a deformed nucleus and in the pure SU (3) Linking the atomic nucleus with dilute gases of ultracold atoms thus offers interesting possibilities for furthering our understanding of nuclear structure. Indeed, the ideas of phase transitions and condensates have been extended to fermionic matter in the form of an -particle condensation [6], which has profound implications in nucleosynthesis. Another example is the description of halo nuclides, where the alpha phase transition is favored over pairing in the dilute nuclear halo [7]-a striking parallel to Bose-Einstein condensates in dilute gases.Nuclear quantum phase transitions are linked to groundstate binding energies within the framework of the IBM [1] (for more detailed discussion in the experimental context, see also [8][9][10]). The ground-state binding energy reflects the net result of all interactions at work in the nucleus and its minimization is decisive for the occupational sequence of the nuclear orbitals. As such, nuclear deformation is highly visible from deep indentations of the mass surface. These features are the manifestations of a first-order quantum phase transition with the critical points defining where the phase transition starts and where it ends [11].In this Letter, we report new mass measurements in the Z ¼ 40 and N ¼ 60 region of the nuclear chart, where one of the most remarkable examples of nuclear shape transition (both for its intensity and its suddenness) is ...

Mass measurements of neutron-rich Cd and Ag isotopes were performed with the Penning trap mass spectrometer ISOLTRAP. The masses of 112,[114][115][116][117][118][119][120][121][122][123][124]120,[122][123][124]126,128 Cd, determined with relative uncertainties between 2 × 10 −8 and 2 × 10 −7 , resulted in significant corrections and improvements of the mass surface. In particular, the mass of 124 Ag was previously unknown. In addition, other masses that had to be inferred from Q values of nuclear decays and reactions have now been measured directly. The analysis includes various mass differences, namely the two-neutron separation energies, the applicability of the Garvey-Kelson relations, double differences of masses δV pn , which give empirical proton-neutron interaction strengths, as well as a comparison with recent microscopic calculations. The δV pn results reveal that for even-even nuclides around 132 Sn the trends are similar to those in the 208 Pb region.

The 110 Pd double-beta decay Q-value was measured with the Penning-trap mass spectrometer ISOLTRAP to be Q = 2017.85 (64) keV. This value shifted by 14 keV compared to the literature value and is 17 times more precise, resulting in new phase-space factors for the two-neutrino and neutrinoless decay modes. In addition a new set of the relevant matrix elements has been calculated. The expected half-life of the two-neutrino mode was reevaluated as 1. The recent results on neutrino oscillations [1-4] have revolutionized our understanding of the role played by neutrinos in particle physics and cosmology, in particular by proving that neutrinos have a finite mass. In the quest for a detailed understanding of the neutrino itself, the rare process of double-beta decay offers the most promising opportunity to probe the neutrino character and to constrain the neutrino mass [5,6]. In contrast to neutrino oscillations, which violate the individual flavor-lepton number while conserving the total lepton number, the process of neutrinoless double-beta decay (0νββ-decay) violates total lepton number and is as such, forbidden by the Standard Model of particle physics. Moreover, unlike the observed neutrino-accompanied double-beta decay (2νββ-decay) process, the 0νββ-decay process would imply that the neutrino is a Majorana particle, i.e., its own antiparticle. While the decay spectrum of the 2νββ-decay is continuous, the experimental signal of the 0νββ-decay represents the sum energy of the two electrons at the decay Q-value. The expected half-life of the 0νββ-decay is extremely long and hence, very small event rates are expected. In addition, a high accuracy (below 1 keV) is desirable to properly identify the signal with respect to background. Furthermore, a well-known Q-value allows a precise determination of the phase space of the halflives of the double-beta decay modes. The decay rates of both decay modes are strong functions of the Q-value. 0νββ-decay scales with the fifth power of the Q-value and 2νββ-decay with the eleventh power. Eleven nuclides (