Comparison of S-matrix and WKB methods for half-width calculations

The calculated Q values and half widths of alpha-decay of superheavy elements using both the S-matrix and the WKB methods are analyzed. The calculations are carried out using the microscopically derived alpha-daughter potentials for the parents appearing in the alpha-decay chain of super heavy element (A=277,Z=112). Both the S-matrix and the WKB methods though yield comparable results for smaller, in fact negative log tau(1/2) values, the former is superior. However, for the case of positive log tau(1/2) it is found that the S-matrix method though exact, runs into some numerical difficulties.