High-spin states in ${}^{70}\mathrm{As}$ were studied using the ${}^{55}\mathrm{Mn}({}^{18}\mathrm{O},3n)$ fusion-evaporation reaction at a beam energy of 50 MeV. Prompt $\gamma \text{−}\gamma$ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. A reinvestigation of the known level scheme resulted in the addition of 32 new transitions and the rearrangement of 10 others. The high-spin decay pattern of yrast negative-parity states was modified and enhanced extensively. Spins were assigned based on directional correlation of oriented nuclei ratios. Lifetimes of seven excited states were measured using the Doppler-shift attenuation method. The $B\left(E2\right)$ rates inferred from the lifetimes of states in the yrast positive-parity band imply substantial collectivity, in agreement with the results of previous studies. Substantial signature splitting and large alternations in the $B\left(M1\right)$ strengths were observed in this band as well, supporting the interpretation of an aligned $\pi g_{9/2}\otimes \nu g_{9/2}$ intrinsic configuration for this structure beginning at the lowest $9^{+}$ state. Large-scale shell-model calculations performed for ${}^{70}\mathrm{As}$ reproduce the relative energy differences between adjacent levels and the $B\left(M1\right)$ rates in the yrast positive-parity band rather well, but underestimate the $B\left(E2\right)$ strengths. The $g_{9/2}$ orbital occupancies for the lowest $9^{+}$ state predicted by the shell-model calculations provide additional evidence of a stretched $\pi g_{9/2}\otimes \nu g_{9/2}$ configuration for this state.

• Received 3 September 2015
• Revised 21 September 2015

DOI:https://doi.org/10.1103/PhysRevC.92.044325