Evidence for isovector neutron-proton pairing from high-spin states in N = Z 74Rb

High-spin states in the odd-odd N = Z nucleus 37⁷⁴Rb37 were studied using the ⁴⁰Ca(⁴⁰Ca,αnp) reaction. A previously observed odd-spin T = 0 band has been extended to I^π = (31⁺) and an even-spin T = 0 band has been observed for the first time to I^π = (22⁺); both have a π(g9/2)⊗ν(g9/2) structure. A strongly coupled low-spin T = 0, K = 3 band has been interpreted as being based upon a π[312]3/2 ⊗ ν[312]3/2 configuration. Cranked relativistic Hartree-Bogoliubov calculations, which are corrected for the t = 1 np-pair field by restoring isospin symmetry, reproduce the observed spectrum. These new results provide evidence for the existence of an isovector pair field that contains a neutron-proton component with the proper strength for ensuring isospin conservation.