Experimental determination of an Iπ=2- ground state in 72,74Cu

This article reports on the ground-state spin and moments measured in Cu-72,Cu-74 using collinear laser spectroscopy at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. From the measured hyperfine coefficients, the nuclear observables mu(Cu-72) = -1.3472(10)mu(N), mu(Cu-74) = -1.068(3)mu(N), Q(Cu-72) = +8(2) efm(2), Q(Cu-74) = +26(3) efm(2), I(Cu-72) = 2, and I(Cu-74) = 2 have been determined. Through a comparison of the measured magnetic moments with different models, the negative moment reveals a strong pi f(5/2) circle times nu g(9/2) component in the ground-state wave function. Consequently, a negative parity has been assigned to the ground states of Cu-72,Cu-74. Large-scale shell-model calculations illustrate the strong sensitivity of the nuclear moments to configuration mixing and to the effective interaction employed.