Isomeric Character of the Lowest Observed ${4}^{+}$ State in $^{44}\mathrm{S}$

Isomeric Character of the Lowest Observed $4^{+}$ State in ${}^{44}S$

J. J. Parker, IV, I. Wiedenhöver, P. D. Cottle, J. Baker, D. McPherson, M. A. Riley, D. Santiago-Gonzalez, A. Volya, V. M. Bader, T. Baugher, D. Bazin, A. Gade, T. Ginter, H. Iwasaki, C. Loelius, C. Morse, F. Recchia, D. Smalley, S. R. Stroberg, K. Whitmore, D. Weisshaar, A. Lemasson, H. L. Crawford, A. O. Macchiavelli, and K. Wimmer

Phys. Rev. Lett. 118, 052501 – Published 31 January 2017

Abstract

Previous experiments observed a $4^{+}$ state in the $N = 28$ nucleus ${}^{44}S$ and suggested that this state may exhibit a hindered $E 2$ -decay rate, inconsistent with being a member of the collective ground state band. We populate this state via two-proton knockout from a beam of exotic ${}^{46}{Ar}$ projectiles and measure its lifetime using the recoil distance method with the GRETINA $γ$ -ray spectrometer. The result, $76 (14)_{stat} (20)_{syst} ps$ , implies a hindered transition of $B (E 2; 4^{+} \to 2_{1}^{+}) = 0.61 (19)$ single-particle or Weisskopf units strength and supports the interpretation of the $4^{+}$ state as a $K = 4$ isomer, the first example of a high- $K$ isomer in a nucleus of such low mass.

Received 3 April 2016

DOI:https://doi.org/10.1103/PhysRevLett.118.052501

Physics Subject Headings (PhySH)

Collective levels Lifetimes & widths

Nuclear Physics

Authors & Affiliations

J. J. Parker, IV¹, I. Wiedenhöver¹, P. D. Cottle¹, J. Baker¹, D. McPherson¹, M. A. Riley¹, D. Santiago-Gonzalez^1,*, A. Volya¹, V. M. Bader^2,3, T. Baugher^2,3, D. Bazin², A. Gade^2,3, T. Ginter², H. Iwasaki^2,3, C. Loelius^2,3, C. Morse^2,3, F. Recchia², D. Smalley², S. R. Stroberg^2,3,†, K. Whitmore^2,3, D. Weisshaar², A. Lemasson⁴, H. L. Crawford⁵, A. O. Macchiavelli⁵, and K. Wimmer^6,2,‡

¹Department of Physics, Florida State University, Tallahassee, Florida, 32306, USA
²National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
³Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, 48824, USA
⁴Grand Accélérateur National dIons Lourds (GANIL), CEA/DSM-CNRS/IN2P3 Caen, France
⁵Lawrence Berkeley National Laboratory, Nuclear Science Division, 1 Cyclotron Road, Berkeley, California 94720-8153, USA
⁶Department of Physics, Central Michigan University, Mt. Pleasant, Michigan 48859, USA

^*Present address: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
^†Present address: TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3.
^‡Present address: The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.