Spectroscopic study of the high-spin states in 135Pr.

Abstract

An in-beam spectroscopic study of $^{135}\mathrm{Pr}$ was made using a 91 MeV $^{120}\mathrm{Sn}$${(}^{19}$F,4n) reaction. Two positive parity bands were observed based on the ${g}_{7/2}$ proton orbital with (\ensuremath{\pi},\ensuremath{\alpha})=(+,\ifmmode\pm\else\textpm\fi{}(1/2)). A strongly populated negative parity (-,-(1/2)) band was also seen (based on the ${h}_{11/2}$ proton orbital). The unfavored (-,+(1/2)) structure may also be present. In both the positive and negative parity bands the first backbend is attributed to the alignment of two ${h}_{11/2}$ protons on the basis of cranked shell model calculations. The crossing frequency was found to increase in the (-,-(1/2)) band because of blocking of the ${h}_{11/2}$ orbital. The alignment of protons in $^{135}\mathrm{Pr}$ causes a shift of \ensuremath{\gamma} towards \ensuremath{\sim}+10\ifmmode^\circ\else\textdegree\fi{} with nearly collective prolate deformation. Also, there is some evidence for a second backbend and an upbend in the case of positive and negative parity bands, respectively. They could result from the alignment of the ${h}_{11/2}$ neutrons.