An isomer with a half-life of 6$\pm$1 $\mu$s has been observed in the $N=74\mathrm{}$ nucleus ${}^{138}$Gd, populated following the reaction ${}^{106}$Cd${(}^{35}$Cl,${p2n)}^{138}$Gd. The isomer decays via a 583 keV $E1\mathrm{}$ transition with a hindrance per degree of $K$ forbiddenness, $f_{\nu }$=24. This value is similar to the values measured for the $N=74\mathrm{}$ isotones ${}^{134}$Nd and ${}^{136}$Sm but markedly different from that measured for ${}^{130}$Ba. This suggests that there is some change in structure across the $N=74\mathrm{}$ isotones and possible explanations of this feature are discussed.

• Received 19 September 1996

DOI:https://doi.org/10.1103/PhysRevC.55.620