Alpha decay half lives of spherical even-even nuclei: Role of repulsive core

By adding repulsive nuclear potential, in Gaussian shape and double-folding form with different values of repulsive surface diffuseness parameter, to the attractive double-folding nuclear potential (M3Y) the effect of repulsive core on alpha decay half-lives and decay parameters of some even-even alpha emitters were analyzed. Calculations were accomplished using WKB approximation by considering Bohr-Sommerfeld quantization condition. The results showed calculated half-lives with M3Y lay between obtained lower and upper limits by M3Y plus repulsive potential with short-range repulsive diffuseness arep=0.01fm and long-range one arep=0.30fm. As result of crucial role of quantization factor an increasing trend of half-lives were observed by increase of arep. Also good coincidence between theory and experiment was observed for a distinct arep which highlights the formation of alpha particle near surface of parent nucleus.