title: Results of a Direct Search Using Synchrotron Radiation for the Low-Energy (229)Th Nuclear Isomeric Transition.
abstract: We report the results of a direct search for the (229)Th (I(π)=3/2(+)←5/2(+)) nuclear isomeric transition, performed by exposing (229)Th-doped LiSrAlF(6) crystals to tunable vacuum-ultraviolet synchrotron radiation and observing any resulting fluorescence. We also use existing nuclear physics data to establish a range of possible transition strengths for the isomeric transition. We find no evidence for the thorium nuclear transition between 7.3 eV and 8.8 eV with transition lifetime (1-2) s≲τ≲(2000-5600)  s. This measurement excludes roughly half of the favored transition search area and can be used to direct future searches.
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Jeet
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Schneider
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Scott T
authors.initials: ST
authors.lastname: Sullivan
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Wade G
authors.initials: WG
authors.lastname: Rellergert
authors.affiliation: Nuclear Security and Isotope Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Saed
authors.initials: S
authors.lastname: Mirzadeh
authors.affiliation: AC Materials, Inc., 756 Anclote Road, Tarpon Springs, Florida 34689, USA.
authors.forename: A
authors.initials: A
authors.lastname: Cassanho
authors.affiliation: AC Materials, Inc., 756 Anclote Road, Tarpon Springs, Florida 34689, USA.
authors.forename: H P
authors.initials: HP
authors.lastname: Jenssen
authors.affiliation: Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Leninskie gory, Moscow 119991, Russia.|Nuclear Safety Institute of Russian Academy of Science, Bol'shaya Tulskaya 52, Moscow 115191, Russia.
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Tkalya
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Hudson