First measurements of g factors in the even Kr isotopes

The g factors of the $2_1^{+}$ and $4_1^{+}$ states in ${}^{78,80,82,84,86}\mathrm{Kr}$ have been measured for the first time, using Coulomb excitation of isotopic Kr beams and the transient field technique. The measured g factors of $2_1^{+}$ states in ${}^{78,80,82}\mathrm{Kr}$ are well described, in both magnitude and progression with neutron number, by the IBA-II model. Whereas the lighter isotopes show a dominant collective structure with g factor values close to $Z/A,$ the large ${g(2\mathrm{}}_1^{+})=1.12\mathrm{}(14)\mathrm{}$ value of ${}^{86}\mathrm{Kr},$ with its closed $N=50\mathrm{}$ shell, is unequivocally dominated by specific proton configurations. The g factor of the $2_1^{+}$ state in ${}^{84}\mathrm{Kr},$ with two holes in the ${1g}_{9/2}$ neutron orbit, reflects both proton and neutron components in the wave function. In addition, the lifetimes of several $2_1^{+}$ and $4_1^{+}$ states were remeasured by the Doppler shift attenuation method, yielding values which, in some cases, differ from those in the literature.