TABLE OF CONTENTS The stripping reaction and its inverse, the pickup reaction, are among the most important, especially for nuclear spectroscopy. The spins and parities of an enormous number of nuclear states have been determined through the analysis of these reactions. They were instrumental in confirming the shell-model description of nuclei, and they provide a direct measure of the single-particle character of nuclear states, as will become evident.
The existence of a direct reaction mechanism, which is distinct from compound nucleus formation and decay, was first recognized by Butler (1950, 1951), based on his interpretation of data on the (d, p) reaction. The early estimates of the distortion effects made by Horowitz and Messiah (1953) and by Butler and Austern (1954) were soon followed by Tobocman's (1954) complete formulation and extensive numerical calculations.
The general form of the DWBA amplitude to which we must now give explicit meaning is
| (7.1) |  |
where W is the statistical weight of the direct terms (see Chapter 5). The reaction is denoted by
| (7.2) |  |
From the definition (3.6) we have
| (7.3) |  |
This full interaction is seldom if ever evaluated. One may argue that V pA should have the general effect that is described by the one-body optical potential U p and that the difference
| (7.4) |  |
may therefore be neglected. From the meaning ascribed to ? ? and ? ?, they take the particular forms
| (7.5) |  |
| (7.6) |  |
where A refers to the nucleon coordinates and spins, X
