Nuclear structure in 16O measured with (e,e´γ) coincident electron scattering
Deininger, John R.
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https://hdl.handle.net/2142/18842
Description
Title
Nuclear structure in 16O measured with (e,e´γ) coincident electron scattering
Author(s)
Deininger, John R.
Issue Date
1996
Doctoral Committee Chair(s)
Nathan, Alan M.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
nuclear structure
coincident electron scattering
nuclear transition currents
collective excitations
Language
en
Abstract
Some long-standing problems in nuclear structure were studied in 160 using the
( e,e'1) coincident electron scattering probe. Data at two momentum transfers ( q =
0.35 and 0.51 fm-1) were obtained using the MUSL-2A accelerator at the University
of Illinois. The photons were detected using a new BaF 2 detector array optimized for
( e,e'1) experiments.
For the first time, we succeeded in sensing the vorticity in the nuclear transition
currents characterizing collective excitations in doubly closed shell nuclei. This observation was achieved by studying the transverse-longitudinal form factor ratios for
the excitations to the 2+ (6.92 MeV) and 3- (6.13 MeV) states of 160. At the same
time, we established the relative sign of the two form factors for both transitions.
Both relative signs were found to be positive, in agreement with the Siegert limit.
We have demonstrated that the transverse-longitudinal form factor ratio in the
isospin-forbidden transition to the 1- (7.12 MeV) state has crossed zero at very low
momentum transfer. This result lends credence to theoretical speculation of a minimum in the longitudinal form factor resulting from iso spin mixing. However the
same results indicate a significant vorticity component in the transition current, which could in principle lead to a destructive interference in the transverse form factor, a
possibility which has not been investigated theoretically.
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