Competition between α- and β+-decay modes for unstable even-even nuclei

alpha-decay and beta-decay are two important decay modes involving different interactions and mechanisms in physics. The competition between alpha-and beta(+)-decay modes for unstable neutron-deficient even-even nuclei is investigated. It is found that the alpha- and beta(+)-decay energies play an important role in their competition. An analytical relationship between the decay energies and branching ratios is presented, which is useful for experimentalists to estimate the main decay channel of unstable nuclei before experiments. The calculated decay branching ratios agree with the experimental data for most nuclei. Predictions of alpha-decay branching ratios of some unstable even-even nuclei are also made for future experiments.