Six isotopes of element 103, with mass numbers 255 through 260, have been studied by means of $\alpha$-particle spectroscopy. The half-lives of the nuclides, and the energies and the intensities of their main $\alpha$-particle groups were observed to be:

A large number of target-projectile combinations were used in synthesizing the lawrencium isotopes. Representative excitation curves for producing the nuclides are displayed. Upper limits for decay by electron capture have been determined. $\alpha$-decay hindrance factors have been calculated using the spin-independent equations of Preston. The $\alpha$-decay energy systematics of the heaviest elements is discussed.

• Received 17 March 1971

DOI:https://doi.org/10.1103/PhysRevC.4.632

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.