Beck T, Werner V, Pietralla N, Bhike M, Cooper N, Friman-Gayer U, Isaak J, Jolos R V, Kleemann J, Papst O, Tornow W, Bernards C, Crider B P, Ilieva R S, Löher B, Mihai C, Naqvi F, Pascu S, Peters E E, Prados-Estevez F M, Ross T J, Savran D, Vanhoy J R, Zilges A
Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA.
Phys Rev Lett. 2020 Aug 28;125(9):092501. doi: 10.1103/PhysRevLett.125.092501.
The size of a ΔK=0 M1 excitation strength has been determined for the first time in a predominantly axially deformed even-even nucleus. It has been obtained from the observation of a rare K-mixing situation between two close-lying J^{π}=1^{+} states of the nucleus ^{164}Dy with components characterized by intrinsic projection quantum numbers K=0 and K=1. Nuclear resonance fluorescence induced by quasimonochromatic linearly polarized γ-ray beams provided evidence for K mixing of the 1^{+} states at 3159.1(3) and 3173.6(3) keV in excitation energy from their γ-decay branching ratios into the ground-state band. The ΔK=0 transition strength of B(M1;0_{1}^{+}→1_{K=0}^{+})=0.008(1)μ_{N}^{2} was inferred from a mixing analysis of their M1 transition rates into the ground-state band. It is in agreement with predictions from the quasiparticle phonon nuclear model. This determination represents first experimental information on the M1 excitation strength of a nuclear quantum state with a negative R-symmetry quantum number.
