TY - THES U1 - Dissertation / Habilitation A1 - Breitenfeldt, Martin T1 - Mass measurements on short-lived Cd and Ag nuclides at the online mass spectrometer ISOLTRAP N2 - In the present work, mass determinations of the eleven neutron-deficient nuclides (99-109)Cd, of ten neutron-rich silver nuclides (112-114,121,123)Ag, and seven neutron-rich cadmium nuclides (114,120,122-124,126,128)Cd are reported. Due to the clean production of the neutron-deficient nuclides it was possible to reduce the experimental uncertainties down to 2 keV, whereas the measurements of neutron-rich nuclides were hampered by the presence of contaminations from more stable In and Cs nuclides. In the case of 99Cd and 123Ag the masses were determined for the first time and for the other nuclides the mass uncertainties could be reduced by up to a factor of 50 as in the case of 100Cd. In the case of a potential isomeric mixture as for (115,117,119)Ag and 123Cd, where no assignment to either the ground state or the excited state was possible, the experimental results were adjusted accordingly. Afterwards all results were included in the framework of the atomic-mass evaluation and thus linked and compared with other experimental data. In the case of the neutron-deficient Cd nuclides a conflict between the mass values obtained in the present work and those published by the JYFLTRAP group could be solved by performing an atomic-mass evaluation. These mass measurements are an important step towards an understanding of the physics of the rp process that will enable a more reliable determination of the composition of the produced material at A = 99. It has been shown that the mass of 99Cd strongly affects the A = 99 production in an X-ray burst model, and that uncertainties have been significantly reduced from more than an order of magnitude to about a factor of 3. The dominant source of uncertainty is now the mass of 100In. In principle, other uncertainties will also contribute. These include those of masses of lighter Cd isotopes, where similar rp-process branchpoints occur and which might affect feeding into the 99Cd branchpoint. In addition, nuclear reaction rate uncertainties will also play a role. However, as reaction rates affect branchings in a linear fashion, while mass differences enter exponentially, mass uncertainties will tend to dominate. Also, which reaction rates are important depends largely on nuclear masses. For example, for low Sp(100In) a (p,γ)-(γ,p) equilibrium will be established between 99Cd and 100In and the 100In(p,γ) reaction rate would affect the A = 99 production, while for larger Sp(100In) the 99Cd(p,γ) reaction rate might be more relevant. Therefore, the mass uncertainties should be addressed first. The presented results are relevant for any rp-process scenario with a reaction flow through the 99Cd region. Here, an X-ray burst model has been used to investigate in detail the impact of the present measurements on such an rp process. The νp process in core collapse supernovae might be another possible scenario for an rp process in the 99Cd region. It it is planed to also explore whether in that case mass uncertainties have a similar impact on the final composition. On the neutron-rich side of the valley of stability for the Cd and Ag chains of nuclides, the r process has not yet been reached. Further technical development on suppression of contaminants are required. This includes improvements on the ISOLDE side, e.g., by improving the selectivity of the transfer line or on the ISOLTRAP setup by implementing an electrostatic ion beam trap for a fast and efficient isobaric selection. Nevertheless the obtained results contribute to the knowledge of nuclear structure. The trends in the two-neutron separation-energy S2n and the interaction between the last neutrons and last protons ΔVpn were corrected to more smooth evolutions, as already seen in other regions of the nuclear chart. The strongest corrections have been observed for even-N nuclides, were more new experimental data are available. Thus, new measurements on odd-N nuclides are suggested. This also is underlined by the trends observed in the Garvey-Kelson relations for the neutron-rich Cd nuclides. Furthermore, it has been shown, that the prominent structure of the ΔVpn for an entire chain of nuclides including inflexion points can be reproduced by using simple relations between quantum numbers of the occupied orbits. This approach connects ten values for each nuclide with only one adjusted parameter. This has been investigated for 63 ΔVpn values of even-even nuclides in the vicinity of Z = 50 and 50 ≤ N ≤ 82. The simple model works remarkably well for the elements Cd, Sn, and Te. Small deviation have been observed for the Xe and Pd nuclides which were explained with the limitations of the model to the vicinity of the close shells, where the nuclides have only few valence protons and neutrons. N2 - In der vorliegenden Arbeit werden die Messungen an elf neutronenarmen Nukliden (99-109)Cd, an zehn neutronenreichen Silbernukliden (112-114,121,123)Ag und an sieben neutronenreichen Cadmiumnukliden (114,120,122-124,126,128)Cd vorgestellt. Aufgrund einer sauberen Produktion der neutronenarmen Nukliden war es möglich die exprimentellen Unsicherheiten bis auf 2keV zu verringern, wärend die Messungen an den neutronenreichen Nukliden durch die Präsenz von stabilen In und Cs Kontaminationen behindert wurden. Für die Nuklide 99Cd und 123Ag konnten die Massen zum ersten mal experimentell bestimmt werden un für die anderen Nuklide war es möglich die Unsicherheiten um bis zu einen Faktor 50 zu verringern wie für das 100Cd. Für den Fall von einer potentiell präsenten isomeren Kontamination wie für (115,117,119)Ag und 123Cd, wo es nicht möglich war zwischen dem isomeren und dem Grundzustand zu unterscheiden, wurden die Ergebnisse entsprechend angepasst. Danach wurden alle Ergebnisse in die AME (atomic-mass evaluation) eingearbeitet und so mit anderen experimentellen Daten verbunden und verglichen. Für die neutronenarmen Cd-Nuklide konnten ein Konflikt zwischen den hier vorgestellten und denen von der JYFLTRAP-Gruppe veröffentlichten Ergebnissen durch eine AME gelöst werden. Diese Massenmessungen sind ein wichtiger Schritt zum Verständnis der dem rp-Prozess zu grunde liegenden Physik, welche eine verläßlichere Bestimmung der produzierten Materialzusammensetzung bei A=99 ermöglicht. Es wurde gezeigt, dass die Masse vom 99Cd die A=99-Produktion in einem "X-ray burst" Modell stark beeinflusst und dass die Unsicherheiten von über einer Größenordnung auf etwa eine Faktor 3 reduziert wurde. Die verbleibende Unsicherheit wird durch den Massenwert vom 100In und von den leichteren Cd-Nukliden erzeugt. Die aus dem benutzten Modell gewonnen Ergebnisse geben einen Anhaltspunkt für die Korrektur der Unterproduktion von Mo und Rh p-Nukliden. Zu einer genaueren Aussage werden weitere Massenmessungen benötigt, die allerdings zuvor noch technische Entwicklungen zur Kontaminationsunterdrückung vorraussetzen. Zusätzlich tragen die erhaltenen Ergebnisse zum Verständnis der Kernstruktur bei. Die Verläufe der zwei-Neutronen-Separationsenergie und der Wechselwirkung der letzten beiden Neutronen mit den letzten beiden Protonen ΔVpn wurden begradigt. Des weiteren wurden die signifikanten Strukturen mit Wendepunktberhalten der ΔVpn in der Mitte der Neutronenschale 50 ≤ N ≤ 82 um den Protonenschalenabschluss bei Z = 50 mittels eines einfachen Überlappmodell unter Einbeziehung des Paarungsformalismus erklärt. KW - Massenspektrometrie KW - Cadmium KW - Silber KW - Nukleosynthese KW - Kernstruktur Y2 - 2009 U6 - https://nbn-resolving.org/urn:nbn:de:gbv:9-000666-2 UN - https://nbn-resolving.org/urn:nbn:de:gbv:9-000666-2 ER -