Reduced alpha widths for nuclei withN≥84,Z≤84

The reduced alpha widths of even-even nuclei with N{≥}84,Z{≤}84 display a systematic behavior with only few anomalies. The widths were deduced from the known alpha-decay half-lives and branching ratios, with penetration factors calculated from realistic cluster wave functions. Predictions are reported for the half-lives of naturally occurring long-lived nuclei as well as the half-lives and branching ratios of short-lived proton-rich nuclei away from the line of beta stability.