Quadrupole Moment of a High-Spin Yrast Trap in Gd 147

Static quadrupole interactions of three $^{147}\mathrm{Gd}$ isomers in single crystals of hexagonal gadolinium have been observed. The quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation ($\ensuremath{\beta}\ensuremath{\sim}0.2$) for the 500-ns high-spin yrast trap.