Possible 'stapler' band in 109Ag nucleus

High-spin states of 109Ag have been studied using the 7Li + 110Pd reaction at a beam energy of 46 MeV. A negative-parity band decaying to the ground-state band by several new linking transitions is established. Meanwhile, seven new E2 crossover transitions of this band are observed, thereby confirming the spin-parity assignment and ordering of the dipole transitions above the Iπ = 19/2− level. A low energy γ-ray transition of 88 keV is found and placed at the bottom of the negative-parity band, and thus the Iπ = 17/2− level is tentatively assigned as the lowest observed state of this band. Experimental excitation energies and total angular momenta of the negative-parity band are compared with the predictions of self-consistent titled axis cranking relativistic mean-field theory with a three-quasiparticle configuration of πg9/2−1⊗νh11/2(g7/2/d5/2)−1. Based on the theoretical description and the analyses of the angular momentum coupling, this negative-parity dipole band is suggested as a 'stapler' band. By investigating the angular momentum components, it is found that the valence nucleons in the low-j orbitals play an active role in the 'stapler' mechanism.