Neutron-proton pairing correlations in medium mass N≃Z nuclei

The pair structure and the average pairing gaps of realistic wave functions obtained within the complex Excited Vampir variational approach are investigated in order to evaluate the neutron-proton pairing correlations at low and high spins in medium mass N similar or equal to Z nuclei, The number of isovector J(pi) = 0(+) pairs is calculated for the lowest few 0(+) states in two chains of nuclei in the A similar or equal to 70 mass region. The results indicate the dominant role played by the isovector neutron-proton pairing correlations in the structure of odd-odd N = Z nuclei and the reduction of their importance with increasing neutron excess in even-even nuclei. The evolution of particular isovector and isoscalar pairs with increasing angular momentum is analyzed for the odd-odd N = Z nucleus Rb-74 and the even-even N = Z nucleus Kr-72, It turns out that in the nucleus Rb-74 the neutron-proton correlations play an essential role for the alignment of the yrast positive-parity even-spin band. (C) 1999 Elsevier Science B.V.