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Wobbling motion in 187 Au
Presented By: Nirupama Sensharma / Nirupama.Sensharma.1@nd.edu
Nirupama Sensharma is a graduate student working in the experimental low energy nuclear physics group at the University of Notre Dame. Her work focuses on using gamma spectroscopic techniques to study the exotic phenomena exhibited by triaxial nuclei. Her PhD research is based on investigating the rare processes of wobbling and chirality in the triaxial 135Pr and 187Au nuclei as well as looking for other regions in the nuclear chart where triaxiality is expected. In addition to nuclear physics research, she is an avid supporter of Nuclear Energy and has founded an initiative (Nuclear Energy - The Better Energy) to promote awareness about the peaceful uses of Nuclear Energy within society by organizing informational campaigns and outreach events. As the founder, she supervises an international team of 9 members based in US, India, France, Germany and Spain and serves as the editor-in-chief of a bimonthly magazine and regularly writes/edits articles and newsletters published by the team for over 900 subscribers.
Abstract
The rare phenomenon of nuclear wobbling motion has already been established in the A~160 and the A~130 regions. Based on observations of significant triaxiality at low spins in the A~190 region, we have extended our investigation of wobbling motion to the 187 Au nucleus. The experiment was performed using the Gammasphere array at the Argonne National Laboratory and the 174 Yb( 19 F,6n) 187 Au reaction was used to populate the levels of interest. Detailed analysis has revealed two separate wobbling structures built on (πh 9/2 ) 1 and (πh 11/2 ) -1 configurations. The wobbling nature of the associated bands has been verified by angular distribution measurements showing a ΔI = 1, E2 nature of the n w+1 → n w connecting transitions, where n w is the wobbling phonon number. Also, large ratios between the reduced E2 transition probability B(E2) out for the ΔI = 1 linking transitions and those for the in-band ΔI = 2 transitions, B(E2) in have been established for the wobbling bands. A most interesting aspect of the results is that the two wobbling structures have been found to exhibit different types of wobbling viz. transverse and longitudinal: if the odd quasiparticle aligns perpendicular (parallel) with the axis with the maximum moment of inertia of the triaxial rotor, the arrangement gives rise to a transverse (longitudinal) wobbler [1]. The wobbling modes are identified by the variation of the wobbling energy with the angular momentum. All but one of the observed wobblers exhibit transverse wobbling. 187 Au is the case not only of the first cleanly established longitudinal wobbler [2], but also of the coexistence of both forms of wobbling in the same nucleus, a phenomenon never observed, or even envisaged, prior to this work. Calculations in the framework of the Particle Rotor Model (PRM) have been found to be in good agreement with the observed results. [1] S. Frauendorf and F. Dönau, Phys. Rev. C 89, 014322 (2014). [2] N. Sensharma et al., Phys. Rev. Lett. 124, 052501 (2020). Download AbstractHosted By
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