We have studied isotopes of element 104 formed by bombarding ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ions. ${}_{}{}^{257}{}_{}{}^{}104$ and ${}_{}{}^{259}{}_{}{}^{}104$ were positively identified by milking their daughters, ${}_{}{}^{253}{}_{}{}^{}\mathrm{No}$ and ${}_{}{}^{255}{}_{}{}^{}\mathrm{No}$. ${}_{}{}^{257}{}_{}{}^{}104$ is a 4.5-sec alpha-particle activity with a complex spectrum; ${}_{}{}^{259}{}_{}{}^{}104$ is likewise an alpha emitter with a half-life of 3 sec. ${}_{}{}^{258}{}_{}{}^{}104$ is tentatively identified as an 11-msec spontaneous-fission activity.

• Received 5 May 1969

DOI:https://doi.org/10.1103/PhysRevLett.22.1317

This article appears in the following collection:

Transuranium Elements and the Physical Review

This collection marks the 150th anniversary of Dmitri Mendeleev’s discovery of the Periodic Table of Elements.