Executive Summary : | The structure of the negative parity bands in odd-A nuclei near A = 130 has drawn great attention as they exhibit some very abnormal properties. There were four negative parity bands observed in odd-A Xe-Ba nuclei systematically. The yrast sequences were explained in terms of coupling between a h_11/2 neutron with the triaxially deformed core. However, the observed signature splitting in these bands was found large and constant as a function of mass number. It was explained in terms of a large contribution from triaxial deformation, but, it is difficult to understand why a nucleus adjusts its shape to keep the signature splitting constant. The yrare bands were assumed to arise due to the coupling between a h_11/2 neutron with the gamma-vibration of the core. Interestingly, the signature inversion was reported in these bands even at lower spin, but no such inversion was reported in the gamma band of the core. Some theoretical calculation predicts the existence of wobbling mode in Xe nuclei with aligned high-j particles. Consequently, longitudinal wobbling was identified experimentally in 127Xe. This work may serve as a testing ground for such theoretical works. Wobbling mode at lower angular momentum was reported in odd-A 127Xe, 135Pr, 105Pd, 133La and 133Ba, based on negative parity h_11/2 orbital. To investigate the above-mentioned problem, the gamma-ray spectroscopy of 125Xe (odd-N) and 129Cs (odd-Z) is planned, using alpha-induced fusion-evaporation reactions. An array HPGe cover detectors will be used as the detector set-up. This array can work as a gamma-ray polarimeter and is hence capable to identify the electric or magnetic nature of a gamma-ray. The electromagnetic properties of a gamma-ray can clearly tell about the existence of wobbling mode. Therefore, this work can solve the long-standing puzzle on the structure of negative parity bands in triaxial nuclei in the A ~ 130 region. How the gamma-vibration of the even-even Xe-Ba nuclei converts into the wobbling mode in odd-A Xe-Ba nuclei can also be addressed from the outcome of this work. Results of the theoretical model calculations can also be verified experimentally from the outcome of this project. |