TABLE OF CONTENTS The three principal assumptions underlying the DWBA were discussed in Chapter 5. They are as follows:
The transfer is assumed to take place directly from the initial to final state. All particles except those actually transferred are assumed to remain in their original states.
The wave function for the relative motion between the partners in the reaction is assumed to be correctly described by the optical potential model, even in the interior region, which enters most crucially for reactions.
The reaction is assumed to be sufficiently weak that it can be treated in lowest order.
Clearly there are conceivable nuclear states for which the cross section would vanish under the first assumption. Figure 17.1 illustrates, in an idealization, just such a situation. The first two states of the nucleus A+1 can be reached by transferring a particle into the single-particle states j and j ?, respectively, whereas all other nucleons remain in their original state. The third state, however, cannot be produced in this way. Instead, it can be produced only if the core nucleons A are excited either before or after the transfer. More generally, if its structure is a? 2(A)? j(1)+b? 0(A)? j, then it can be reached both directly through the component in the wave function with amplitude b and indirectly by the two paths indicated in the figure through the component in the wave function with amplitude a. Because there is no way of distinguishing between...
