Hur Joonseok, Aude Craik Diana P L, Counts Ian, Knyazev Eugene, Caldwell Luke, Leung Calvin, Pandey Swadha, Berengut Julian C, Geddes Amy, Nazarewicz Witold, Reinhard Paul-Gerhard, Kawasaki Akio, Jeon Honggi, Jhe Wonho, Vuletić Vladan
Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
JILA, NIST and University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2022 Apr 22;128(16):163201. doi: 10.1103/PhysRevLett.128.163201.
Optical precision spectroscopy of isotope shifts can be used to test for new forces beyond the standard model, and to determine basic properties of atomic nuclei. We measure isotope shifts on the highly forbidden ^{2}S_{1/2}→^{2}F_{7/2} octupole transition of trapped ^{168,170,172,174,176}Yb ions. When combined with previous measurements in Yb^{+} and very recent measurements in Yb, the data reveal a King plot nonlinearity of up to 240σ. The trends exhibited by experimental data are explained by nuclear density functional theory calculations with the Fayans functional. We also find, with 4.3σ confidence, that there is a second distinct source of nonlinearity, and discuss its possible origin.
