First observation of the drip line nucleus ${}^{140}\mathrm{Dy}:$ Identification of a $7\hspace{0.5em}\mu \mathrm{s}\hspace{0.5em}K$ isomer populating the ground state band

A new $7\hspace{0.5em}\mu \mathrm{s}$ isomer in the drip line nucleus ${}^{140}\mathrm{Dy}$ was selected from the products of the ${}^{54}\mathrm{Fe}$ $(315\mathrm{}\hspace{0.5em}\mathrm{MeV}{)+}^{92}\mathrm{Mo}$ reaction by a recoil mass spectrometer and studied with recoil-delayed $\gamma -\gamma$ coincidences. Five cascading $\gamma$ transitions were interpreted as the decay of an $I^{\pi }{=8\mathrm{}}^{-}$ $\{\nu {9/2}^{-}\left[514\right]\otimes \nu {7/2}^{+}\left[404\right]\}$ K isomer $(T_{1/2}=7.0\mathrm{}(5\left)\mathrm{}\hspace{0.5em}\mu \mathrm{s}\right)$ via the ground-state band. The probability of proton emission from ${}^{141}\mathrm{Ho}$ to the $0^{+}$ ground state and to the $2^{+}$ excited state in ${}^{140}\mathrm{Dy}$ is discussed.