Band crossings in ${}^{166}\mathrm{Ta}$

High-spin states in the odd-odd nucleus ${}^{166}\mathrm{Ta}$ are investigated through the $5n$ channel of the ${}^{51}\mathrm{V}+{}^{120}\mathrm{Sn}$ reaction. Four new bands are observed and linked into the previous level scheme. Configurations for the bands are proposed, based on measured alignments and $B(M1)/B(E2)$ transition strength ratios.

Figure 1

Level scheme of ${}^{166}\mathrm{Ta}$. All spins and parities must be regarded as tentative (see text). The width of the arrows are proportional to the relative $\gamma$-ray intensity observed in the experiment.

Figure 2

Example spectra for bands 1, 2, and 3 in ${}^{166}\mathrm{Ta}$. (a) Summed spectrum of triple gates with any two $M1$ transitions below $I=18$ in band 1 with the 680-keV transition. The left and right insets display the highest energy transitions in the $\alpha =0$ and 1 signatures, respectively. (b) Summed spectrum for band 2 where any two transitions of the 207-, 217-, 265-, or 282-keV lines were gated with the 143- and 588-keV transitions. The peak denoted by a circle is from band 1. The insets were created in a similar gating technique as those in (a) to show the highest transitions in the $\alpha =0$ (left inset) and $\alpha =1$ (right inset) sequences. (c) Summed spectrum of band 3 triple gated on any two $M1$ transitions between $I=16$ and 21 with the 543/545-keV lines.

Figure 3

Alignment vs rotational energy for (a) bands 1, 4, and 5; (b) band 2; and (c) band 3 in ${}^{166}\mathrm{Ta}$. In (a) and (b), the $\nu i_{13/2}$ and $\nu E$ bands from ${}^{165}\mathrm{Hf}$ are shown for reference, respectively.

Figure 4

Experimental and theoretical $B(M1)/B(E2)$ ratios for bands (a) 1, (b) 2, and (c) 3 in ${}^{166}\mathrm{Ta}$. Theoretical calculations are displayed as lines with the configurations denoted in each panel. At higher spins, the calculations include an additional two $i_{13/2}$ neutrons (see text).