Multiple magnetic rotational bands based on proton alignment in ${}^{143}\mathrm{Eu}$

High-spin dipole structures in ${}^{143}\mathrm{Eu}$ have been studied via the fusion-evaporation ${}^{116}\mathrm{Cd}$ $({}^{31}\mathrm{P}$, $4n)$ reaction at a beam energy of 148 MeV using a clover detector array (Indian National Gamma Array). The parity of the two observed dipole bands has been firmly established from linear polarization measurements. Level lifetimes of these bands have been measured using the Doppler shift attenuation method. The drop in $B\left(M1\right)$ values with spin exhibits a clear signature of the magnetic rotational character of these two bands. Configurations were assigned to the bands in the framework of the shears mechanism with the principal axis cranking model calculation. Alignment of an additional proton in the $h_{11/2}$ orbital gives rise to the unique observation of a large increase in the $B\left(M1\right)$ values for the higher-lying band.

Figure 1

The partial level scheme of ${}^{143}\mathrm{Eu}$ obtained in the present work. The $\gamma$-ray energies are given in keV and the width of the arrows are proportional to the intensities of the transitions. The energies are rounded off to the nearest keV.

Figure 2

Representative spectra along with theoretically fitted line shapes for the dipole transitions (a) 275.5 keV and (b) 361.3 keV of the dipole band DB I in ${}^{143}\mathrm{Eu}$.

Figure 3

Representative spectra along with theoretically fitted line shapes for the dipole transitions (a) 303.2 keV and (b) 408.8 keV of the dipole band DB II in ${}^{143}\mathrm{Eu}$. Calculated line shape of the $\gamma$ transitions, contaminant peaks and total line shapes are represented by the blue, olive, and red curves, respectively.

Figure 4

Representative spectra along with theoretically fitted line shapes (see text) obtained from a single Ge crystal for the dipole transitions (a) 275.5 keV and (b) 361.3 keV of the dipole band DB I in ${}^{143}\mathrm{Eu}$.

Figure 5

The comparison of experimental results for (a) spin $\left(I\right)$ and (b) $B\left(M1\right)$ values, represented by solid (DB I) and open (DB II) squares, with the SPAC model calculations for DB I (solid blue line) and DB II (solid red line) in ${}^{143}\mathrm{Eu}$. The solid olive stars are the deduced $B\left(M1\right)$ values for DB1 and DB2 in ${}^{141}\mathrm{Eu}$, taken from Ref. [18].

Figure 6

Contour plots of the TRS calculations for the assumed configurations of the dipole bands (a) DB I and (b) DB II in ${}^{143}\mathrm{Eu}$. The rotational frequency $\left(\hslash \omega \right)$ for both calculations is 0.210 MeV. The energy difference between two contours is 0.400 MeV.