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Spectroscopy of neutron-rich germanium and krypton isotopes - A quest of triaxiality

Lettmann, Marc (2018):
Spectroscopy of neutron-rich germanium and krypton isotopes - A quest of triaxiality.
Darmstadt, TUprints, Technische Universität, [Online-Edition: http://tuprints.ulb.tu-darmstadt.de/7382],
[Ph.D. Thesis]

Abstract

This work covers the spectroscopic analysis of 84,86,88Ge and 94,96Kr isotopes populated by different reactions within the SEASTAR campaign 2015. The experimental setup and the data analysis are described in detail. This analysis includes necessary functionality checks and calibrations of the detectors along the beam line. In-flight γ-ray spectroscopy of 84,86,88Ge was performed after various knock-out reactions. γ-spectroscopy of neutron-rich 88Ge was performed for the first time. The Doppler-corrected γ-ray spectra are analyzed with simulated lineshapes of occurring transitions. In total 16 transitions are observed ten of which so far unknown. New level schemes for 86,88 Ge are proposed based on the observed transition intensities and systematics of neighboring Ge isotopes. The obtained level schemes are compared to state-of-the-art theoretical calculations. The assignment of a 3⁺ state of 86Ge agrees with new shell model and SCCM predictions. The agreement to the level orderings from the collective model by Davydov and co-workers points to an amount of rigid triaxiality in 86Ge. This is the first indication of rigid triaxiality in an unstable, neutron-rich nucleus. In addition, an analysis of reaction cross sections, as well as cross sections for the excitation of a particular state is performed. This data set represents one of the first results for this newly-accessible region of the nuclear chart. Furthermore, 84,86Ge and 94,96Kr are investigated after (p,p') reactions, which excite different states than the knock-out reactions. These states are candidates for octupole 3⁻ states, which are the first benchmark for the octupole degree of freedom in this exotic region. The obtained (p,p') cross sections of the 2⁺₁ states from 94,96Kr are compared to the transition strength known from literature based on the deformation length.

Item Type: Ph.D. Thesis
Erschienen: 2018
Creators: Lettmann, Marc
Title: Spectroscopy of neutron-rich germanium and krypton isotopes - A quest of triaxiality
Language: English
Abstract:

This work covers the spectroscopic analysis of 84,86,88Ge and 94,96Kr isotopes populated by different reactions within the SEASTAR campaign 2015. The experimental setup and the data analysis are described in detail. This analysis includes necessary functionality checks and calibrations of the detectors along the beam line. In-flight γ-ray spectroscopy of 84,86,88Ge was performed after various knock-out reactions. γ-spectroscopy of neutron-rich 88Ge was performed for the first time. The Doppler-corrected γ-ray spectra are analyzed with simulated lineshapes of occurring transitions. In total 16 transitions are observed ten of which so far unknown. New level schemes for 86,88 Ge are proposed based on the observed transition intensities and systematics of neighboring Ge isotopes. The obtained level schemes are compared to state-of-the-art theoretical calculations. The assignment of a 3⁺ state of 86Ge agrees with new shell model and SCCM predictions. The agreement to the level orderings from the collective model by Davydov and co-workers points to an amount of rigid triaxiality in 86Ge. This is the first indication of rigid triaxiality in an unstable, neutron-rich nucleus. In addition, an analysis of reaction cross sections, as well as cross sections for the excitation of a particular state is performed. This data set represents one of the first results for this newly-accessible region of the nuclear chart. Furthermore, 84,86Ge and 94,96Kr are investigated after (p,p') reactions, which excite different states than the knock-out reactions. These states are candidates for octupole 3⁻ states, which are the first benchmark for the octupole degree of freedom in this exotic region. The obtained (p,p') cross sections of the 2⁺₁ states from 94,96Kr are compared to the transition strength known from literature based on the deformation length.

Place of Publication: Darmstadt
Publisher: TUprints
Divisions: 05 Department of Physics
05 Department of Physics > Institute of Nuclear Physics
05 Department of Physics > Institute of Nuclear Physics > Experimentelle Kernphysik
05 Department of Physics > Institute of Nuclear Physics > Experimentelle Kernphysik > Experimental Nuclear Structure Physics with Exotic Ion Beams
Date Deposited: 20 May 2018 19:55
Official URL: http://tuprints.ulb.tu-darmstadt.de/7382
URN: urn:nbn:de:tuda-tuprints-73821
Referees: Pietralla, Prof. Dr. Norbert and Aumann, Prof. Dr. Thomas
Refereed / Verteidigung / mdl. Prüfung: 16 April 2018
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Alternative Abstract:
Alternative abstract Language
Diese Arbeit behandelt die spektroskopische Analyse von 84,86,88Ge und 94,96Kr Isotopen, die durch verschiedene Reaktionen im Rahmen der SEASTAR Kampagne 2015 bevölkert wurden. Der experimentelle Aufbau und die Analyse werden detailliert beschrieben. Diese Analyse beinhaltet die nötigen Funktionstests und Eichungen der Detektoren entlang der Strahlführung. γ-Spektroskopie von 84,86,88Ge wurde nach verschiedenen Knock-Out-Reaktionen im Flug durchgeführt. Zum ersten Mal wurde neutronenreiches 88Ge spektroskopiert. Die Doppler-korrigierten γ-Spektren wurden durch simulierte Linienformen der auftretenden Übergänge analysiert. Insgesamt wurden 16 Übergange beobachtet, zehn dieser Übergänge waren bisher unbekannt. Begründet durch die beobachteten Intensitäten und die Systematiken der benachbarten Germaniumisotope werden neue Levelschemata für 86,88Ge vorgeschlagen. Die erhaltenen Levelschemata werden mit modernsten theoretischen Berechnungen verglichen. Die Zuweisung eines 3⁺ Zustands von 86Ge stimmt mit neuen Schalenmodell- und SCCM-Vorhersagen überein. Die Übereinstimmung zu den Zustandsanordnungen des kollektiven Modells von Davydov und Kollegen weist auf einen Grad der Triaxialität in 86Ge hin. Dies ist der erste Hinweis auf starre Triaxialität in einem instabilen, neutronenreichen Kern. Zusätzlich wird eine Analyse der Reaktionswirkungsquerschnitte und der Wirkungsquerschnitte für die Anregung eines bestimmten Zustands durchgeführt. Dieser Datensatz repräsentiert eine der ersten Ergebnisse in dieser neu zugänglichen Region der Nuklidkarte. Außerdem werden 84,86Ge und 94,96Kr nach (p,p')-Reaktionen, die im Vergleich zu Knock-Out-Reaktionen andere Zustände anregen, untersucht. Diese Zustände sind Kandidaten für 3⁻ Oktupolzustände, die der erste Bezugspunkt für den Oktupolfreiheitsgrad in dieser exotischen Region sind. Die erhaltenen (p,p')-Wirkungsquerschnitte der 2⁺₁ Zustände von 94,96Kr werden mit den aus der Literatur bekannten Übergangsstärken mit Hilfe der Deformationslänge verglichen.German
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