Hindered decays from a non-yrast four-quasiparticle isomer in164Er

The half-life of a ${K}^{\\ensuremath{\\pi}}={12}^{+}$ isomer in ${}^{164}$Er has been measured to be 68(2) ns, and new decay pathways have been identified. These include highly $K$-forbidden $\\ensuremath{\\gamma}$-ray transitions directly to the ground-state rotational band, with reduced hindrance values that can be compared with those found for heavier nuclides. The new data support the interpretation that the level density is a key variable in determining $K$-forbidden transition rates.