FIZIKA B 20 (2011) 4, 319-330
EXCITATION OF THE LOW-LYING ISOMERIC LEVEL IN 229Th
KINNEY H. KIMa, and GEORGE M. IRWINb
aPhysics Department, NCCU, Durham, NC 27707, U. S. A.
bPhysics Department, Lamar University, Beaumont, TX 77710, U. S. A.
Received 31 January 2011 ; Accepted 14 December 2011
Online 19 March 2012
Gamma-ray spectroscopy measurements have revealed
the presence of an isomeric excited state in 229Th only
(3.5±1.0) eV above the ground state, and recent measurements
with a high resolution detector have resulted in the value of
(7.6±0.5) eV. The state is of interest due to the unique
atomic-nuclear interactions which should govern its decay.
The state is also of interest as excitation of the level
allows the study of processes important in the development
of gamma-ray lasers. Although a small number of experiments
have been done in an attempt to observe the de-excitation
of the isomeric level populated following alpha decay of
233U, the results remain controversial and inconclusive,
mainly due to ambiguities in samples used by various
researchers. To date no attempts have been made to excite
the low-lying level from the ground state of 229Th, nor
has there been a systematic study of 233U in various
sample forms with suitable uranium control isotopes to
look for evidence of the decay of the low-lying level
consistent with theoretical predictions. We present a
comparison of some possible excitation techniques,
including the resonant (Mössbauer effect) and non-resonant
(broadband) methods, and propose some possible experiments.
PACS numbers: 23.35.+g, 33.45.+x
UDC 539.166, 539.144, 76.80.+y
Keywords: isomeric state in 229Th, atomic-nuclear interaction