Band structures in ${}^{101}\mathrm{Pd}$

Excited states in the ${}^{101}\mathrm{Pd}$ nucleus were investigated through the ${}^{75}\mathrm{As}({}^{31}\mathrm{P},2p3n)$ fusion-evaporation reaction at $E_{\mathrm{lab}}=125$ MeV by using the Indian National Gamma Array spectrometer equipped with 21 clover Ge detectors. The level scheme is considerably extended for medium spin values. New positive-parity band structures in ${}^{101}\mathrm{Pd}$ have been studied within the framework of the projected shell model and are found to undergo transition from single quasiparticle to high-$K$ three quasiparticle configuration after band crossing, i.e., from principal-axis rotation to tilted-axis rotation. The negative-parity band structures are discussed in the framework of the hybrid version of tilted-axis cranking shell model calculations. The observed alignment gain in the lowest excited $\nu h_{11/2}$ negative-parity band results from successive ${\left(\nu g_{7/2}\right)}^2$ and ${\left(\pi g_{9/2}\right)}^2$ pair alignments. The higher excited negative-parity bands are reproduced for the $\nu \left[h_{11/2}{(g_{7/2}/d_{5/2})}^2\right]$ and ${\left(\pi g_{9/2}\right)}^{-2}\otimes \nu h_{11/2}$ configurations.

Figure 1

Total projection spectrum of $E_{\gamma }-E_{\gamma }$ matrix showing the prominent $\gamma$ rays of various nuclei populated in the present experiment.

Figure 2

Level scheme of ${}^{101}\mathrm{Pd}$ obtained from the present work. Energies of $\gamma$ rays and levels are given in keV. The width of the arrows is proportional to the relative $\gamma$ ray intensity. The level structures built on levels labeled L1, L2, and L3 of bands B1 and B2 are shown separately.

Figure 3

The double-gated $\gamma$-ray coincidence spectra in ${}^{101}\mathrm{Pd}$ generated with coincidence gates on $\gamma$ rays as labeled. Unlabeled insets show the high-energy part of the respective labeled main spectra. The spectra depict (a) transitions in dipole structure in the upper part of band B2, (b) transitions in band B3, (c) transitions in the extended lower spin part of band B5, and (d) transitions in bands B2, B6, and B7. The spectrum shown in the inset of panel (a) infers that the 368 keV transition has no link with upper part of band B1 that is inconsistent with placement by Sugawara et al. [22]. The peaks marked (*) correspond to contamination from other nuclei.

Figure 4

The double-gated $\gamma$-ray coincidence spectra showing transitions of the positive-parity band B6.

Figure 5

Experimental excitation energy vs spin plots for (a) the positive-parity bands B1, B2, B6, and B7 and (b) the negative-parity bands B3–B5 in ${}^{101}\mathrm{Pd}$. The excitation plot for the ground-state band in ${}^{100}\mathrm{Pd}$ [8, 35] is compared with that of the $\nu h_{11/2}$ band (B3) in ${}^{101}\mathrm{Pd}$ in panel (b). The spin values for the ground-state band are shifted by $5.5\hslash$ and the excitation energy for the $11/2^{-}$ bandhead state in $\nu h_{11/2}$ band (B3) is shifted to zero.

Figure 6

Experimental alignment ($i_x$) plots for (a) the positive-parity bands B1, B2, B6, and B7, and (b) the negative-parity bands B3–B5 in ${}^{101}\mathrm{Pd}$, and (c) the $\nu d_{5/2}$ and $\nu g_{7/2}$ bands in odd-$A {}^{99,101}\mathrm{Pd}$ isotopes [7]. Bands C1 and C2 in panel (c) correspond to the positive-parity high-spin-coupled part in the ${}^{101}\mathrm{Pd}$ (band B2) and ${}^{99}\mathrm{Pd}$ [7], respectively.

Figure 7

Experimental Routhian ($e^{\prime }$) plots for (a) the positive-parity bands B1, B2, B6, and B7, and (b) the negative-parity bands B3–B5 in ${}^{101}\mathrm{Pd}$.

Figure 8

Band diagram for the positive-parity bands for ${}^{101}\mathrm{Pd}$ depicting the angular-momentum projected bands from one- and three-quasiparticle states. For clarity, only the lowest projected bands are shown and in the numerical calculations, projection has been performed from fifty intrinsic states.

Figure 9

Comparison of the calculated level energies for the positive-parity bands with the present experimental data for ${}^{101}\mathrm{Pd}$.

Figure 10

Comparison of experimentally observed spin vs frequency plots with the tac model calculations for various configurations for the negative-parity (a) band B3 and (b) bands B4 and B5 in ${}^{101}\mathrm{Pd}$.