Study of two phonon octupole vibrations in 146Gd
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Date
2013
Authors
Journal Title
Journal ISSN
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Publisher
University of Zululand
Abstract
Recent measurements of double octupole vibrational states in 146Gd have resulted in the
need of deeper studies of such excitations. A state with J =6+ at 3485 keV has been
suggested as the two-phonon octupole excitation in 146Gd. A 6+ ! 3 ! 0+ cascade of
E3
-ray transitions from this state supports this interpretation
This work aims at investigating this 6+ state and the other missing members of the octupole
quartet are sought in order to accurately characterize the two-phonon octupole vibrations
in nearly-spherical nuclei. The
coincidence experiment, with the 144Sm( , 2n)146Gd
fusion-evaporation reaction at a beam energy of 26.3 MeV, was performed to produce the
146Gd nucleus. The experiment was performed using the AFRODITE array at iThemba
Laboratory for Acceletor-Based Sciences (LABS), South Africa. Eight clover detectors were
used, with four at 90 and four at 135 , and they were surrounded by the BGO shields
for compton suppression. With the highly e cient AFRODITE array, the experiment
provided good quality data which was sorted into
matrices. From these matrices, the
total projection spectrum was obtained. A gate on a 382 keV
-ray transition was made to
see if the suggested 1905 keV
-ray transition from the J = 6+ state to the J = 3 state
will be observed. From the 382 keV gated spectrum, there was no evidence of the 1905 keV
-ray transition. The branching ratios of the 826 and 502 keV transitions were measured
and the limit to the intensity of the 1905 keV peak has been set. The limit was set to 6
intensity for the unobserved 1905 keV
-ray transition . Our work show no evidence of the
1905 keV
-ray transition and thus no octupole vibrations in 146Gd. However, limitations
in the sensitivity of our experiment may leave an open door to further investigate the
existence of the two-phonon octupole excitation in 146Gd nucleus.
Description
Dissertation submitted in partial fulfillment of the requirements for the
degree of Master of Science in the Department of Physics and Engineering at the University of Zululand, South Africa, 2013.
Keywords
Phonon octupole vibrations