Showing papers by "Peter Möller published in 2010"

New Type of Asymmetric Fission in Proton-Rich Nuclei

Abstract: A very exotic process of {beta}-delayed fission of {sup 180}Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-{beta}-decay daughter nucleus {sup 180}Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two {sup 90}Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for {beta}-delayed fission of {sup 180}Tl is 3.6(7)x10{sup -3}%, approximately 2 orders of magnitude larger than in an earlier study.

Half-lives and branchings for β-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process

Abstract: The {beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {beta}-delayed neutron emission (P{sub n} values) for {sup 74}Co (18{+-}15%) and {sup 75-77}Ni (10{+-}2.8%, 14{+-}3.6%, and 30{+-}24%, respectively) for the first time, and remeasured the P{sub n} values of {sup 77-79}Cu, {sup 79,81}Zn, and {sup 82}Ga. For {sup 77-79}Cu and for {sup 81}Zn we obtain significantly larger P{sub n} values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of {sup 75}Co (30{+-}11 ms) and {sup 80}Cu (170{sub -50}{sup +110} ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.

My journey to the superheavy island with szymanski, nilsson, nix, and swiatecki from lysekil to the present

Abstract: We discuss the great theoretical insights on nuclear stability that emerged in the late 1960ies, especially the realization that observable nuclei might include a superheavy island 20+ protons beyond uranium with 92 protons. However, we now realize that the early models were not sufficiently quantitative to yield definite conclusions. Further groundwork for such models was laid in the 1970ies. Around 1980 more quantitative, global and universal models appeared and together with experimental advances the mapping of the superheavy island, or as it turns out now, continent started in earnest. We review these early developments and conclude with some examples of our current insights. In particular, 1) some theoretical models do have predictive capabilities for nuclear properties such as ground-state masses, shapes, and half-lives 10 or more neutrons and protons away from previously known regions and 2) the superheavy island may be a continent connected to the actinides by a narrow land bridge; the continent itself may extend from about proton number Z = 110 to Z = 120 or slightly beyond.

[Current aspects of the pathology and differentiation of extranodal marginal zone B-cell lymphoma, MALT-Type, and gastrointestinal diffuse large B-cell lymphoma].

Abstract: The marginal zone B-cell lymphoma, MALT-type (MZBL, MT) is a low-grade B-cell lymphoma which is predominantly localised in the stomach with a typical morphology and cytogenetic pattern. The coexistence of a diffuse large B-cell lymphoma (DLBCL) with an MZBL, MT in the gastrointestinal tract is defined as a composite lymphoma (ComL) and represents a fascinating model of lymphoma progression. In this review we focus on current aspects regarding the molecular characterisation of MZBL, MT and gastrointestinal DLBCL and their mutual relationships.

Reassignment of the genus Thalassobathia from Bythitidae to Ophidiidae (Teleostei, Ophidiiformes) based on the first reported males

Abstract: Le genre Thalassobathia Cohen, 1963 de l'ordre des Ophidiiformes avait ete place dans le groupe des genres vivipares d'ophidioides (Cohen, 1963), et ulterieurement dans la famille des Bythithidae par Cohen et Nielsen (1978). Les 30 specimens connus a ce jour etaient identifies comme des femelles, des immatures ou bien de sexe indetermine. Cependant, l'etude histologique des gonades de deux de ces specimens (235 et 270 mm LS) a montre que tous les deux etaient des mâles. Les caracteres diagnostiques des Bythitidae vivipares, c'est-a-dire la presence d'un capuchon genital et d'un organe copulateur, sont absents chez ces specimens; de ce fait, nous proposons de replacer le genre Thalassobathia dans la famille ovipare des Ophidiidae.

Electron capture reactions in neutron star crusts: deep heating and observational constraints

Abstract: We compute the nucleosynthesis in the outer crust of an accreting neutron star, starting with an rp-process distribution of nuclei and integrating to neutron-drip density. Our reaction network includes temperature-dependent continuum electron capture rates and realistic sources of heat loss by thermal neutrino emission from the crust and core. We show that, in contrast to previous calculations, electron captures into excited states and subsequent γ-emission significantly increases the local heat deposited into the outer crust. This heating raises the crust temperature and reduces the critical accreted mass needed for unstable ignition of 12C + 12C, which is thought to trigger superbursts observed from some accreting neutron stars. As a result, the superburst recurrence time is shortened, which brings calculations of the superburst ignition depth closer to that inferred from observations.