Fusion of the systemZr90+Zr90

Cross sections for compound residues from the fusion reaction ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$+${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ were measured. No "extra push" is necessary to describe the data. Below the fusion barrier, the cross section decreases much faster than observed previously in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$-induced fusion reactions with tin and samarium targets. The present data are incompatible with recently published data for the same system.