Bulg. J. Phys. vol.42 no.4 (2015), pp. 572-582

Current Experimental Techniques of Lifetime Measurements and Their Importance for the Nuclear Structure

S. Pascu1, D. Bucurescu1, Gh. Căta-Danil2, C. Costache1, N.M. Florea1, D.G. Ghiţă1, T. Glodariu1, A. Ionescu1, C. Mihai1, R. Mihai1, I. Mitu1, N. Mărginean1, R. Mărginean1, A. Negret1, C.R. Niţă1, A. Olăcel1, L. Stroe1, R. Şuvăilă1, A. Şerban1, S. Toma1, A. Turturică1, N.V. Zamfir1
1National Institute for Physics and Nuclear Engineering, R-77125, Bucharest-Magurele, Romania
2Politehnica University of Bucharest, 060042, Bucharest, Romania
Abstract. One of the most important topics in nuclear spectroscopy is measuring the lifetimes of excited states. These quantities are related to the reduced transition probabilities, which are rather sensitive to details of the intrinsic structure of the states. Therefore, such measurements represent a crucial test for various theoretical models which address different regions of the nuclear chart. Lifetimes of excited states cover many orders of magnitude, but typically they are in the range below nanosecond. Consequently, several methods allowing lifetime measurements in these regions have been developed. The ROmanian array for SPectroscopy in HEavy ion REactions (ROSPHERE) is a γ-spectrometer which was designed specifically to allow for sensitive lifetime measurements down to the picosecond range. ROSPHERE is a new 4π high-resolution γ-ray detector array which was installed at the Bucharest 9 MV tandem accelerator. The setup consists of up to 25 detectors and it is typically used in a mixed combination of high-purity Ge detectors and fast LaBr3:Ce scintillation detectors. The multi-detector setup can be coupled with a state of the art plunger device allowing for lifetime measurements by employing the Recoil Distance Doppler Shift (RDDS) or in-beam Fast Electronic Scintillation Timing (FEST) technique. This work reports on two experiments performed on >sup>168Yb and 150Gd illustrating the methods and how this helps our understanding of the complex nuclear phenomena including nuclear deformation.

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