Reaction Mechanisms of Pair Transfer

Abstract

The mechanisms of nuclear transfer reactions are described for the transfer of two nucleons from one nucleus to another. Two-nucleon overlap functions are defined in various coordinate systems, and their transformation coefficients given between coordinate systems. Post and prior couplings are defined for sequential transfer mechanisms, and it is demonstrated that the combination of 'prior-post' couplings avoids nonorthogonality terms, but does not avoid couplings that do not have good zero-range approximations. The simultaneous and sequential mechanisms are demonstrated for the 124 Sn(p,t) 122 Sn reaction at 25 MeV using shell-model overlap functions. The interference between the various simultaneous and sequential amplitudes is shown.

Application of an ab initio S matrix to data analysis of transfer reactions to the continuum populating Be11

“…It can be resumed with the findings of Ref. [22] and [23] which agree with the whole previous literature. In the first paper it is stated that " the simultaneous and nonorthogonal contributions [of the two neutrons to transfer] are in antiphase, so that the contribution corresponding to the coherent superposition of these two amplitudes tend to cancel.…”

“…[23] shows that the two-step, successive, transfer also occurs in a correlated fashion. If we were to use the model of [23] for example, the different possible quantum mechanical paths associated with the population of different intermediate states of 10 Be+ 17 O in our case, would be summed coherently. Also, the different terms (successive transfer, simultaneous transfer, and non-orthogonality contribution) would represent different amplitude contributions to the second-order process, to be added coherently to get the second order cross section.…”

“…On the other hand Ref. [23] shows that the two-step, successive, transfer also occurs in a correlated fashion. If we were to use the model of [23] for example, the different possible quantum mechanical paths associated with the population of different intermediate states of 10 Be+ 17 O in our case, would be summed coherently.…”

“…Also, the different terms (successive transfer, simultaneous transfer, and non-orthogonality contribution) would represent different amplitude contributions to the second-order process, to be added coherently to get the second order cross section. Their relative importance in a coupled channel model such as that discussed in [23] depends on the arbitrary choice of the reaction representation (prior-prior, post-post, prior-post or post-prior). However in our case because we treat transfer between heavy ions we can use a semiclassical model in which the post and prior representations coincide.…”

Two-particle transfer processes as a signature of shape phase transition in Zirconium isotopes

“…In parallel with the detailed microscopic structure description described above, also the reaction process has been described in microscopic terms. In particular, we have performed second order DWBA calculations with the code FRESCO [16,17]. Therefore the reaction mechanism includes the "correlated" sequential single-particle transfer through all intermediate states in the A+1 odd system, the simultaneous transfer of the two neutrons and non-orthogonality terms.…”