An i_13/2 intruder band in ¹³⁹Gd

A rotational band of eleven gamma -rays has been observed in ¹³⁹Gd showing an enhanced moment of inertia indicative of a band of higher quadrupole deformation than the low-lying states. This band is believed to be built on a single nu i_13/2 intruder orbital, and extends the systematics of such bands, recently observed in several samarium nuclei (Z=62), to gadolinium (Z=64). An attempt is made to deduce the spins for levels within this band by fitting the extracted moment of inertia with a power expansion in terms of the rotational frequency. This method is also used to deduce the spins for other bands of enhanced deformation in this mass region; the method is shown to reproduce the known spins for the nu i_13/2 intruder bands in the ^135,137Sm isotopes.