X-Ray Identification of Element 104

The daughter x-ray identification technique has been applied to the identification of element 104. The characteristic $K$-series x rays from the $\ensuremath{\alpha}$-decay daughter isotope, nobelium ($Z=102$), have been observed in coincidence with $\ensuremath{\alpha}$ particles from the decay of 4.5-sec $^{257}104$, thus providing an unequivocal determination of the parent atomic number, $Z=104$.