Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 13: Structure and Dynamics of Nuclei IV

HK 13.3: Vortrag

Montag, 14. März 2016, 17:15–17:30, S1/01 A04

Fast-timing lifetime measurement of ^178,180Hf — •Johannes Wiederhold¹, Ralph Kern¹, Volker Werner¹, Norbert Pietralla¹, Nico Marginean², Raluca Marginean², Cristina Roxana Nita², Sorin Pascu², Dorel Bucurescu², Dan Mihai Filipescu², Nicoleta Florea², Dan Gabriel Ghita², Constantin Mihai², Razvan Lica², Patrick Regan³, Robert Carroll³, Terver Daniel³, Laila Gurgi³, Ralitsa Ilieva^3,4, Nathan Cooper⁴, and Farheen Naqvi⁴ — ¹IKP, TU-Darmstadt — ²IFIN-HH, Bucharest — ³Physics Department at Surrey — ⁴Yale University

Deformed nuclei in the rare earth region should show a saturation of the B(E2;0₁⁺→2₁⁺)-transition strength near the mid-shell. Recent measurements of lifetimes of W-isotopes show discrepancies to literature values and seem to maximize the B(E2)-strength off mid-shell. An analog investigation is done on Hf-isotopes. The lifetimes τ(2₁⁺) of ¹⁷⁸Hf and ¹⁸⁰Hf have been measured using fast electronic scintillation timing (FEST) at the 9 MV tandem accelerator of the IFIN-HH near Bucharest. Excited States of ¹⁸⁰Hf were populated via coulomb excitation and of ¹⁷⁸Hf via β⁺-decay following the reaction ¹⁷⁴Yb(⁷Li,3n)¹⁷⁸Ta. Because the target of ¹⁸⁰Hf was contaminated by 5% of ¹⁷⁸Hf and both isotopes have nearly the same transition energies (ΔE ≤ 1 keV) for the 4₁⁺→2₁⁺- and 2₁⁺→0_gs⁺-transitions, a correction has to be applied using the lifetime of the 2₁⁺-state of ¹⁷⁸Hf. Preliminary results for these lifetimes will be presented. This work was supported by the DFG under the Grant No. SFB 634 and the U.S. DOE Grant No. DE-FG02-91ER40609.