title: Direct detection of the (229)Th nuclear clock transition.
abstract: Today's most precise time and frequency measurements are performed with optical atomic clocks. However, it has been proposed that they could potentially be outperformed by a nuclear clock, which employs a nuclear transition instead of an atomic shell transition. There is only one known nuclear state that could serve as a nuclear clock using currently available technology, namely, the isomeric first excited state of (229)Th (denoted (229m)Th). Here we report the direct detection of this nuclear state, which is further confirmation of the existence of the isomer and lays the foundation for precise studies of its decay parameters. On the basis of this direct detection, the isomeric energy is constrained to between 6.3 and 18.3 electronvolts, and the half-life is found to be longer than 60 seconds for (229m)Th(2+). More precise determinations appear to be within reach, and would pave the way to the development of a nuclear frequency standard.
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: von der Wense
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Benedict
authors.initials: B
authors.lastname: Seiferle
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.|Helmholtz-Institut Mainz, 55099 Mainz, Germany.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Laatiaoui
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Jürgen B
authors.initials: JB
authors.lastname: Neumayr
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Maier
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Hans-Friedrich
authors.initials: HF
authors.lastname: Wirth
authors.affiliation: Helmholtz-Institut Mainz, 55099 Mainz, Germany.|Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mokry
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.|Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Runke
authors.affiliation: Helmholtz-Institut Mainz, 55099 Mainz, Germany.|Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Eberhardt
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.|Helmholtz-Institut Mainz, 55099 Mainz, Germany.|Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Christoph E
authors.initials: CE
authors.lastname: Düllmann
authors.affiliation: Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Norbert G
authors.initials: NG
authors.lastname: Trautmann
authors.affiliation: Ludwig-Maximilians-Universität München, 85748 Garching, Germany.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Thirolf