Shell-model calculations using realistic interactions reveal that the ground and low-lying yrast states of the N = Z nucleus (92)(46)Pd are mainly built upon isoscalar neutron-proton pairs, each carrying the maximum angular momentum J = 9 allowed by the shell 0g(9/2), which is dominant in this nuclear region. This structure is different from that found in the ground and low-lying yrast states of all other even-even nuclei studied so far. The low-lying spectrum of excited states generated by such correlated neutron-proton pairs has two distinctive features: (i) the levels are almost equidistant at low energies and (ii) the transition probability I -> I - 2 is approximately constant and strongly selective. This unique mode is shown to replace normal isovector pairing as the dominant coupling scheme in N = Z nuclei approaching the doubly magic nucleus (100)Sn.
QC 20110907