Approximation of reduced width amplitude and application to cluster decay width

Abstract: We propose a simple method to approximately evaluate reduced width amplitude (RWA) of a two-body spinless cluster channel using the norm overlap with the Brink-Bloch cluster wave function at the channel radius. The applicability of the present approximation is tested for the $<sup>{16}$O+$\alpha$ channel in $<sup>{20}$Ne as well as the $\alpha$+$\alpha$ channel in $<sup>8$Be. The approximation is found to be reasonable to evaluate the RWA for states near the threshold energy and it is useful to estimate the $\alpha$-decay width of resonance states. The approximation is also applied to $<sup>9$Li, and the partial decay width of the $<sup>6$He($0<sup>+_1$)+$t$ channel is discussed.