Role of neutrons in the coexistence of magnetic and antimagnetic rotation bands in 107 Cd

Negative parity high-spin states of 107Cd have been investigated using the reaction 94Zr(18O,5n), from the γ -ray coincidence events recorded by the Indian National Gamma Array. A magnetic dipole (M1) band structure was established for the first time in this nucleus decaying to the low-spin states via several paths. Lifetimes of five in-band levels in this band have been measured using the Doppler shift attenuation method. The experimentally deduced B(M1) values are found to decrease with increasing spin. The experimental observations, interpreted by the tilted axis cranking calculations, suggest that the M1 band is developed from the shears mechanism based on the 5qp configuration π (g−2 9/2) ⊗ ν(h11/2g 7/2), which is then crossed by another 5qp configuration π (g−2 9/2) ⊗ ν(h11/2). The semiclassical model of the shears mechanism also reasonably reproduces the decreasing trend of the observed B(M1) values as a function of spin, supporting the above interpretation. The present work highlights the unique coexistence of both magnetic and antimagnetic (observed by us earlier) rotation bands in one nucleus arising from the same proton configuration, but different neutron configurations.