The characteristics of the low-lying levels of ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$, ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$, and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$ have been investigated via multiple Coulomb excitation effected by bombarding isotopically enriched thick targets with 36 to 42 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions. These measurements allowed the excitation of the $2^{+}$, $2^{+\prime }$, $0^{+\prime }$, and $4^{+}$ levels in all nuclei. The $E2\mathrm{}$ transition values of the $\gamma$ rays deexciting the $2^{+\prime }$ and $4^{+}$ levels to the $2^{+}$ states are compared with those recently measured in ${}_{}{}^{66}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$. A close inspection of this set of data clearly reveals a change of nuclear properties between $N=38\mathrm{}$ and $N=40\mathrm{}$. This is in agreement with the possible existence of a shape transition around $N=40\mathrm{}$.

NUCLEAR REACTIONS ${}_{}{}^{70,72,74,76}{}_{}{}^{}\mathrm{Ge}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, {}_{}{}^{16}{}_{}{}^{}\mathrm{O}_{}^{\prime }{}_{}{}^{}\gamma )$, $E=36\mathrm{} \mathrm{to} 42$ MeV; measured $I_{\gamma }$, $E_{\gamma }$; deduced $B\left(E\lambda \right)$, $B\left(M1\mathrm{}\right)\mathrm{}$, $J$, $T_{\frac{1}{2}}$. Enriched targets.

• Received 4 August 1980

DOI:https://doi.org/10.1103/PhysRevC.22.2420