Rotational Spectrum ofTm171

The gamma rays emitted from ${\mathrm{Tm}}^{171}$ following the ${\mathrm{Er}}^{171}$ beta decay have been measured with the twometer curved-crystal spectrometer and a semicircular beta-ray spectrometer, enabling a comparison of the nuclear levels and rotational parameters for the ${\mathrm{Tm}}^{171}$ ground-state band with the corresponding levels and parameters of ${\mathrm{Tm}}^{169}$. The measured gamma rays have the following energies in kev: 5.06±0.05, 12.40±0.05, 111.63±0.02, 116.69±0.03, 124.03±0.03, 210.62±0.15, 284.9±0.7, 295.97±0.15, 308.37±0.15. In comparing the rotational parameters, a slight increase in the deformation of ${\mathrm{Tm}}^{171}$ over that of ${\mathrm{Tm}}^{169}$ is noted. The relatively large change in the decoupling parameter ($a=-0.8563\mathrm{}$) for ${\mathrm{Tm}}^{171}$ compared with that of ${\mathrm{Tm}}^{169}$ cannot be accounted for entirely by the small change in nuclear deformation.