Proton Orbital [541]1/2 and Backbending in 178W

The microscopic mechanism of nine experimentally observed bands in¹⁷⁸W is investigated using the particle-number conservingmethod of the cranked shell model with monopole and quadrupole paring interactions. The experimental results, including the moments of inertia and angular momentum alignments of nine bands in ¹⁷⁸W, are reproduced well by the particle-number conserving calculations, in which no free parameter is involved. Calculationsdemonstrate that occurrence of sharp backbending comes mainly fromthe contribution of high-j intruder orbitals νi13/2 or πh11/2 and their interference effect with orbitals near the Fermi surface. The ω variation of the occupation probability ofeach cranked orbital and the contribution to moment of inertia fromeach cranked orbital are analyzed.