Pion exchange and the reactions $np \rightarrow pn, \bar{p}p \rightarrow \bar{n}n$ and $\gamma p \rightarrow \pi^{+}n$

A simple phenomenological model involving the interference of the pion pole with a nonspecified background is used to fit the high-energy experimental data of np to pn, gamma p to pi /sup +/n and pp to nn. In the energy range investigated, the s-dependence is only kinematical. For the form factor of the pion-nucleon coupling constant, a slope of about 2.3 (GeV/c)/sup -2/ is found, whereas the slope of the pion trajectory is quite small. A comparison of charge exchange and photoproduction indicates that factorization holds. (18 refs).