A systematic theoretical investigation of the quadrupole and octupole collective properties across the Gd isotopic chain is performed employing a quadrupole-octupole axially symmetric model. These nuclei recently attracted significant attention following the revelation that the maximum octupole collectivity in this region is located at ${}^{150}\mathrm{Gd}$. The model parameters are optimized by fitting to the low-lying positive and negative-parity energy levels, as well as to known $E0, E1, E2$, and $E3$ transition strengths. Our primary objective is a simultaneous and unified description of quadrupole and octupole collectivity across the even-even Gd nuclei in the $84\le N\le 96$ range, a region that includes the transition from spherical to rotational nuclear shapes. The results show a smooth evolution of the quadrupole deformation, highlighted by a distinct jump at the well-known $N=90$ critical point. The enhancement of quadrupole deformation is also correlated with the loss of non-zero octupole deformation, which is reported only for the lightest ${}^{148,150}\mathrm{Gd}$ nuclei. This translates into a fair agreement with the measured $E3$ strength, predicting a maximum $B\left(E3\right)$ value for the ${}^{152}\mathrm{Gd}$ isotope.

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• Collective levels
• Electromagnetic transitions
• Energy levels
• Nuclear structure & decays
• 150 ≤ A ≤ 189