Structure of dipole bands in doubly odd ${}^{102}\mathrm{Ag}$

Excited states in the transitional doubly odd ${}^{102}\mathrm{Ag}$ nucleus were populated in the ${}^{75}\mathrm{As}({}^{31}\mathrm{P},p3n)$ fusion-evaporation reaction using the 125 MeV incident ${}^{31}\mathrm{P}$ beam. The subsequent deexcitations were investigated through in-beam $\gamma$-ray spectroscopic techniques using the Indian National Gamma Array spectrometer equipped with 21 clover Ge detectors. The level scheme in ${}^{102}\mathrm{Ag}$ has been established up to excitation energy $\sim 6.5$ MeV and angular momentum $19\hslash$. The earlier reported level scheme is considerably extended and modified to result in a pair of nearly degenerate negative-parity dipole bands. Lifetime measurements for the states of these two dipole bands have been performed by using the Doppler-shift attenuation method. The two nearly degenerate bands exhibit different features with regard to kinetic moment of inertia, and the reduced transition probabilities $\mathrm{B}\left(M1\right)$ and $\mathrm{B}\left(E2\right)$, which do not favor these to be chiral partners. These bands are discussed in the framework of the hybrid version of tilted-axis cranking (tac) model calculations and assigned the $\pi g_{9/2}\otimes \nu h_{11/2}$ and $\pi g_{9/2}\otimes \nu h_{11/2}{(d_{5/2}/g_{7/2})}^2$ configurations. The tac model calculations are extended to the nearly degenerate bands observed in the heavier doubly odd ${}^{104–108}\mathrm{Ag}$ isotopes.

Figure 1

Level scheme of ${}^{102}\mathrm{Ag}$ obtained from the present work. Energies of $\gamma$ rays and levels are given in keV. The width of the arrow representing the $\gamma$ transition indicates relative intensity of the $\gamma$ ray.

Figure 2

The double-gated $\gamma$-ray coincidence spectra showing the transitions of bands B1–B5 in ${}^{102}\mathrm{Ag}$. The spectra are generated with coincidence gate on $\gamma$-rays as labeled.

Figure 3

The lineshape fits for the 398 (${10}^{-}\to 9^{-}$) keV and 350 (${11}^{-}\to {10}^{-}$) keV transitions in band B3, and the 237 (${12}^{-}\to {11}^{-}$) keV and 275 (${13}^{-}\to {12}^{-}$) keV transitions in band B4, at various angles with respect to the incident beam direction.

Figure 4

The excitation energy vs spin plots for bands B1 and B2 in ${}^{102}\mathrm{Ag}$, the $\pi g_{9/2}$ band in ${}^{101}\mathrm{Ag}$ [38], and the $\nu d_{5/2}$, $\nu g_{7/2}$, and $\nu h_{11/2}$ bands in ${}^{101}\mathrm{Pd}$ [39, 40]. The spin values in the $\pi g_{9/2}$ band in ${}^{101}\mathrm{Ag}$ (with the $9/2^{+}$ state as bandhead) are shifted by $2.5\hslash$ for comparison with the $\pi g_{9/2}\otimes \nu d_{5/2}$ and $\pi g_{9/2}\otimes \nu g_{7/2}$ bands (with the $7^{+}$ state as bandhead) in doubly odd ${}^{102}\mathrm{Ag}$.

Figure 5

The comparison of the experimental and tac-model-calculated excitation energy vs spin plots for the negative-parity doublet bands in doubly odd (a) ${}^{102}\mathrm{Ag}$, (b) ${}^{104}\mathrm{Ag}$ [13], (c) ${}^{106}\mathrm{Ag}$ [15, 16, 20], and (d) ${}^{108}\mathrm{Ag}$ [18] isotopes.

Figure 6

Experimental Routhian plots for (a) bands B1–B5 in ${}^{102}\mathrm{Ag}$ and the $\pi g_{9/2}$ band in ${}^{103}\mathrm{Ag}$ [41], and (b)–(d) negative-parity doublet bands in doubly odd ${}^{104,106,108}\mathrm{Ag}$ isotopes [13, 15, 16, 18, 20].

Figure 7

Experimental alignment plots for (a) bands B1–B5 in ${}^{102}\mathrm{Ag}$, and (b) the $\pi g_{9/2}$ band in ${}^{101}\mathrm{Ag}$ [38], and $\nu d_{5/2}$, $\nu g_{7/2}$, $\nu h_{11/2}$, and ${\left(\pi g_{9/2}\right)}^{-2}\otimes \nu h_{11/2}$ bands in ${}^{101}\mathrm{Pd}$ [39, 40].

Figure 8

The kinetic moment of inertia comparison of doublet bands in doubly odd ${}^{102–108}\mathrm{Ag}$ [13, 15, 16, 18, 20].

Figure 9

The comparison of the experimental and theoretical reduced transition probabilities, $\mathrm{B}\left(M1\right)$ and $\mathrm{B}\left(E2\right)$, for the main band and the partner band in the (a) ${}^{102}\mathrm{Ag}$, (b) ${}^{104}\mathrm{Ag}$ [13], and (c) ${}^{106}\mathrm{Ag}$ [15, 16, 20] isotopes. The comparison of the experimental and theoretical $\mathrm{B}\left(M1\right)/\mathrm{B}\left(E2\right)$ values for the main band and the partner band in the (d) ${}^{102}\mathrm{Ag}$, (e) ${}^{104}\mathrm{Ag}$ [13], and (f) ${}^{106}\mathrm{Ag}$ [15, 16, 20] isotopes.

Figure 10

The spin $I$ vs frequency $\hslash \omega$ plots for the observed negative-parity doublet bands in (a) ${}^{102}\mathrm{Ag}$, (b) ${}^{104}\mathrm{Ag}$ [13], (c) ${}^{106}\mathrm{Ag}$ [15, 16, 20], and (d) ${}^{108}\mathrm{Ag}$ [18] isotopes. The results of the tac calculations based on different relevant configurations are also shown for comparison.

Figure 11

Plot of energy-staggering parameter $S\left(I\right)=\left[E\right(I)-E(I-1\left)\right]/2I$ for (a)–(d) the doubly odd ${}^{102–108}\mathrm{Ag}$ isotopes [13, 15, 16, 18, 20], and (e), (f) $N=55$ isotones ${}^{98}\mathrm{Tc}$ [7] and ${}^{100}\mathrm{Rh}$ [9] plotted as a function of spin $I\left(\hslash \right)$. The signature inversion spin values are encircled.