The g-factor measurement of the 4$^+_1$ state in $^{70}$Zn

The measurement of the g factors of excited nuclear states provide an indication of their microscopic structure since the g factors are very sensitive to the proton and neutron contributions to the wave functions. Recently, g factors of excited states in the even-even stable Zn nuclei were measured. The measured g factors of their 2$^+_1$ states were generally in good agreement with the results of shell model calculations as well as with the Z/A value, the characteristic of collective behavior. Also studied were the g factors of some 4$^+_1$ states, which are only weakly excited by Coulomb excitation. Possible contributions of $g_{9/2}$ neutrons to the wave function of the 4$^+_1$ states in the Zn isotopes would reduce the g factors of these states. To extend these systematic studies, the 4$^+_1$ state of $^{70}$Zn was populated by the Coulomb excitation, on a C target, of a beam of $^{70}$Zn in inverse kinematics, and its g-factor was studied using the Transient Field technique. The $\gamma$ ray transition energies in $^{70}$Zn have some near-degeneracies which make the extraction of the g-factor of 4$^+_1$ state difficult. Work supported by the U.S. National Science Foundation, U.S.D.O.E under grant DE-FG02-91ER-40609 and by German BMBF under grant number 06KY2051.