Branching ratios of α-decay to excited states of even-even nuclei

We make a systematic calculation on $\alpha$-decay branching ratios to members of ground-state rotational band and to excited $0^{+}$ states of even-even nuclei by a simple barrier penetration approach. The branching ratios to the excited states of daughter nucleus are determined by the $\alpha$-decay energy, the angular momentum of $\alpha$-particle, and the excitation probability of the daughter nucleus. Our calculation covers isotopic chains from Hg to Fm in the mass regions 180$<$A$<$202 and A$\geq$224. The calculated branching ratios of $\alpha$-transitions are consistent with the experimental data. Some useful predictions are made for future experiments.