Bandcrossing of magnetic rotation bands in Pr137

Abstract

The odd mass nucleus Pr137 has been studied to high spins in order to investigate the magnetic rotation phenomenon in mass 130 region using the Sn122(F19,4n)Pr137 reaction at a beam energy of 80 MeV. A known ΔI=1 band has been extended to Jπ=47/2- with the addition of three new transitions. Directional Correlation of Oriented Nuclei (DCO) ratios and linear polarization measurements have been performed to assign the multipolarities of gamma transitions and the spins and parities of the energy levels in this band, now established as the M1 band. The combination of M1 transitions along with cross over E2 transitions have been observed in this band for the first time. The experimentally deduced B(M1)/B(E2) ratios show a decrease with increasing spin after band-crossing suggesting magnetic rotation. TAC calculations for the 3qp: πh11/2 ν(h11/2)-2 configuration reproduce the experimental observations in the lower spin part of the ΔI=1 band and the 5qp: πh11/2(g7/2)2 ν(h11/2)-2 configuration reproduces the ΔI=1 band at higher spins; the crossing of the bands based on the two configuration leads to a back-bending also. Theoretical calculations also support a magnetic rotation nature for both the configurations. © 2007 The American Physical Society.