The projected shell model (PSM) was employed to study the signature inversion of 160Tm and 161Tm isotopes. The Hamiltonian of these isotopes were constructed and solved to obtain the energy levels and the γ -ray transition energies. The rotational bands of the odd–odd 160Tm and odd–even 161Tm isotopes of thulium nucleus were constructed based on the πh 11/ 2 ⊗ υi 13 /2 Nilsson configuration to calculate the kinetic and dynamic moments of inertia, γ -ray transition energy (I = 1) and the staggering parameter (S(I)). Yrast band with two signatures for both isotopes have been extracted and compared with the experimental data. The anomalous splitting and signature inversion occurred due to the quadruple deformation in both isotopes. Analysis of level staggering and signature inversion show that signature inversion for the 160Tm isotope occurs at low spin region, while for the 161Tm isotope, it occured in the intermediate spin region. As expected, zig-zag behaviour and phase transition, as well as signature of energy splitting are clearly indicated in figures showing variation of S(I) and E with spin. This behaviour is more visible for the odd–even 161Tm isotope than for the odd–odd 160Tm isotope. Good agreement between the calculated results and experimental data confirms the success of the PSM model.
