Continuum Strength of Direct Breakup Induced by External Isoscalar Field

New formula to describe the non-resonant background strength in the binary breakup is considered on the basis of the Migdal-Watson (MW) formula. The background strength is assumed to be generated by the direct breakup, which is the one step transition from the initial bound state to the final continuum state. The strength of the direct breakup is evaluated by the complex scaling method (CSM). We have found that the extended MW formula, which is proposed in the present study, nicely reproduces the strength of the direct breakup calculated by CSM. The relation of the parameters newly introduced in the extended MW formula and the spatial size of the initial wave function is also discussed.