Systematics of ground-state quadrupole moments of odd-Adeformed nuclei determined with muonicMx rays

The ground-state quadrupole moments of ¹⁵¹Eu, ¹⁵³Eu, ¹⁵⁹Tb, ¹⁶³Dy, ¹⁶⁷Er, ¹⁷⁷Hf, ¹⁷⁹Hf, ¹⁹¹Ir, and ¹⁹³Ir were determined by measuring the quadrupole hyperfine-splitting energies of muonic M x rays. The results are $Q=0.903(10)e$ b for ¹⁵¹Eu, $Q=2.412(21) e$ b for ¹⁵³Eu, $Q=1.432(8) e$ b for ¹⁵⁹Tb, $Q=2.648(21) e$ b for ¹⁶³Dy, $Q=3,565(29) e$ b for ¹⁶⁷Er, $Q=3.365(29) e$ b for ¹⁷⁷Hf, $Q=3.793(33) e$ b for ¹⁷⁹Hf, $Q=0.816(9) e$ b for ¹⁹¹Ir, and $Q=0.751(9) e$ b for ¹⁹³Ir. The present quadrupole moments, compared with values obtained from electronic-atom hyperfine measurements, show that the Sternheimer correction factors used in the rare-earth electronic-atom analysis are unreliable. Systematics of deformation parameters β₂ calculated from the present quadrupole moments for odd-A nuclei, and from $B(E2)$ values of Coulomb excitation measurements for even-A nuclei, also indicate that the largest deformation change so far known exists between ¹⁵¹Eu and ¹⁵³Eu. Except at the onset of nuclear deformation, the deformation parameters of the odd-A nuclei are quite consistent with those of the even-A neighbors.